Mapping of control information to control channel elements

ABSTRACT

The invention relates to a new structure of a control channel region within a sub-frame of a 3GPP-based based communication system using OFDM in the downlink. This new structure of a control channel region is inter alia particularly suitable for conveying physical downlink control channel information from a donor eNodeB to a relay node. The control channel region is divided in CCEs that have equal size irrespective of the presence of further cell-specific and/or UE-specific reference signals within the control channel region. This is achieved by dividing the control channel region in plural sub-CCEs that are combined to CCEs all having equal size (in terms of resource elements that can be used for the signaling of control information). The control channel region is divided in the frequency domain and/or time domain in a FDM respectively TDM fashion in order to obtain the sub-CCEs.

FIELD OF THE INVENTION

The invention relates to a new structure of a control channel regionwithin a sub-frame of a 3GPP-based based communication system using OFDMin the downlink. This new structure of a control channel region is interalia particularly suitable for conveying physical downlink controlchannel information from a donor eNodeB to a relay node. However, thenew structure of a control channel region within a sub-frame may also beused on the air interface between eNodeBs and user equipments as well asthe air interface between the eNodeBs and relay nodes.

The invention further provides a method for mapping physical downlinkcontrol channel information for a receiving apparatus to control channelelements of a control channel region of a sub-frame of a 3GPP-basedbased communication system using OFDM in the downlink and to a methodfor receiving control information for a receiving apparatus of a3GPP-based communication system using OFDM in the downlink. Moreover,the invention is also related to a transmitting apparatus (e.g. a eNodeBor relay node) and a receiving apparatus (e.g. a relay node or userequipment) that perform the methods.

The invention is inter alia applicable to a 3GPP LTE-A system asstandardized by the 3^(rd) Generation Partnership Project (3GPP).

TECHNICAL BACKGROUND

3GPP Long Term Evolution (3GPP LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology, such as UMTS (Universal Mobile Communications System), arecurrently deployed on a broad scale all around the world. A first stepin enhancing or evolving this technology entails introducing High-SpeedDownlink Packet Access (HSDPA) and an enhanced uplink, also referred toas High Speed Uplink Packet Access (HSUPA), giving a radio-accesstechnology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support to the next decade. Theability to provide high bit rates is a key measure for LTE. The workitem (WI) specification on LTE called Evolved UMTS Terrestrial RadioAccess (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN) is to befinalized as Release 8 (LTE Rel. 8). The LTE system represents efficientpacket-based radio access and radio access networks that provide fullIP-based functionalities with low latency and low cost. The detailedsystem requirements are given in 3GPP TR 25.913, “Requirements forEvolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN),” version 8.0.0,January 2009 (available at http://www.3gpp.org and incorporated hereinby reference).

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8) is subdividedin the time-frequency domain in so-called sub-frames. In 3GPP LTE(Release 8) each sub-frame is divided into two downlink slots as shownin FIG. 1, wherein the first downlink slot comprises the control channelregion (PDCCH region) within the first OFDM symbols. Each sub-frameconsists of a give number of OFDM symbols in the time domain (12 or 14OFDM symbols in 3GPP LTE (Release 8)), wherein each of OFDM symbol spansover the entire bandwidth of the component carrier. The sub-frames thuseach consist of a number of 2·N_(symb) ^(DL) modulation symbolstransmitted on respective N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers as alsoshown in FIG. 2.

Assuming a multi-carrier communication system, e.g. employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”(or “physical resource block”, abbreviated PRB). A physical resourceblock is defined as N_(symb) ^(DL) consecutive OFDM symbols in the timedomain and N_(sc) ^(RB) consecutive subcarriers in the frequency domainas exemplified in FIG. 2. In praxis, the downlink resources are assignedin resource block pairs (or physical resource block (PRB) pairs). Aresource block pair consists of two resource blocks on the samesubcarriers of the sub-frame, i.e. spans N_(sc) ^(RB) consecutivesubcarriers in the frequency domain and the entire 2·N_(symb) ^(DL)modulation symbols of the sub-frame in the time domain. N_(symb) ^(DL)may be either 6 or 7, so that a sub-frame has either 12 or 14 OFDMsymbols in total.

In 3GPP LTE (Release 8), a physical resource block thus consists ofN_(symb) ^(DL)×N_(sc) ^(RB) resource elements, corresponding to one slotin the time domain and 180 kHz in the frequency domain (for furtherdetails on the downlink resource grid, see for example 3GPP TS 36.211,“Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channelsand Modulation (Release 8)”, version 8.9.0, December 2009 section 6.2,available at http://www.3gpp.org and incorporated herein by reference).

The value N_(RB) ^(DL) depends on the downlink transmission bandwidthconfigured in the cell and shall fulfill the relation N_(RB)^(min,DL)≦N_(RB) ^(DL)≦N_(RB) ^(max,DL). Presently, N_(RB) ^(min,DL)=6and N_(RB) ^(max,DL)=110 and represent the smallest and largest downlinkbandwidths, respectively, supported by the current version of thespecifications in 3GPP LTE (Release 8) and 3GPP LTE-A (Release 10)—seebelow. N_(SC) ^(RB) is the number of subcarriers within one resourceblock. For a normal cyclic prefix sub-frame structure, N_(SC) ^(RB)=12and N_(symb) ^(DL)=7 in the current versions of the 3GPP specificationsfor 3GPP LTE (Release 8) and 3GPP LTE-A (Release 10).

In MBSFN operation, the user equipment receives and combinessynchronized signals from multiple cells. In order for MBSFN reception,the user equipment performs a separate channel estimation based on MBSFNReference Signal (MBSFN RS). In order to avoid mixing MBSFN RS and otherreference signals (RSs) in the same sub-frame, certain sub-frames, knownas MBSFN sub-frames, are reserved for MBSFN transmission.

Up to two of the first OFDM symbols within a sub-frame are reserved fornon-MBSFN transmission and the remaining OFDM symbols are used for MBSFNtransmission. In the first up to two OFDM symbols, PDCCH for uplinkresource assignments and PHICH can be transmitted, and the cell specificreference signal is the same as non-MBSFN sub-frames.

The pattern of MBSFN sub-frames in one cell is broadcasted in the SystemInformation (SI) of the cell. UEs, that are not capable of receivingMBSFN, will decode the first up to two OFDM symbols and ignore theremaining OFDM symbols.

MBSFN sub-frame configuration supports both 10 ms and 40 ms periodicity.And sub-frames #0, #4, #5 and #9 cannot be configured as MBSFNsub-frames.

General Structure for Downlink Physical Channels

The general downlink 3GPP LTE (Release 8) baseband signal processingaccording to 3GPP TS 36.211 section 6.3 is exemplarily shown in FIG. 6.Further details on the LTE downlink can be found in 3GPP TS 36.211,section 6. A block of coded bits is first scrambled. Up to two codewords can be transmitted in one sub-frame.

In general, scrambling of coded bits helps to ensure that receiver-sidedecoding can fully utilize the processing gain provided by channel code.For each codeword, by applying different scrambling sequence forneighboring cells, the interfering signals are randomized, ensuring fullutilization of the processing gain provided by the channel code. Thescrambled bits are transformed to a block of complex modulation symbolsusing the data modulator for each codeword. The set of modulationschemes supported by LTE downlink includes QPSK, 16-QAM and 64-QAMcorresponding to 2, 4 or 6 bits per modulation symbol.

Layer mapping and precoding are related to MIMO applications. Thecomplex-valued modulation symbols for each of the code words to betransmitted are mapped onto one or several layers. LTE supports up tofour transmit antennas. The antenna mapping can be configured indifferent ways to provide multi antenna schemes including transmitdiversity, beam forming, and spatial multiplexing. Further the resourceblock mapper maps the symbols to be transmitted on each antenna to theresource elements on the set of resource blocks assigned by thescheduler for transmission. The selection of resource blocks depends onthe channel quality information.

Downlink control signaling is carried out by three physical channels:

-   -   PCFICH to indicate the number of OFDM symbols used for control        signaling in a sub-frame (i.e. the size of the control channel        region)    -   PHICH which carries downlink ACK/NACK associated with UL data        transmission    -   PDCCH which carries downlink scheduling assignments and uplink        scheduling assignments.        Downlink Reception in 3GPP LTE

In 3GPP LTE (Release 8), where there is only once component carrier inuplink and downlink, the PCFICH is sent at a known position within thecontrol signaling region of a downlink sub-frame using a knownmodulation and coding scheme. As the determination of the downlinkresources assigned to the user equipment depends on the size of thecontrol signaling region of the sub-frame, i.e. the number of OFDMsymbols used for control signaling in the given sub-frame, the userequipments needs to decode the PCFICH in order to obtain the signaledPCFICH value, i.e. the actual number of OFDM symbols used for controlsignaling in the sub-frame.

If the user equipment is unable to decode the PCFICH or obtains anerroneous PCFICH value, this PCFICH detection error will result in theuser equipment not being able to correctly decode the L1/L2 controlsignaling (PDCCHs) comprised in the control signaling region, so thatall resource assignments contained therein are lost.

Physical Downlink Control Channel (PDCCH) and

Physical Downlink Shared Channel (PDSCH)

The physical downlink control channel (PDCCH) carries scheduling grantsfor allocating resources for downlink or uplink data transmission. Eachscheduling grant is defined based on Control Channel Elements (CCEs).Each CCE corresponds to a set of Resource Elements (REs). In 3GPP LTE,one CCE consists of 9 Resource Element Groups (REGs), where one REGconsists of four consecutive REs (in the frequency domain) excludingpotential REs of reference signals.

The PDCCH for the user equipments is transmitted on the first N_(symb)^(PDCCH) OFDM symbols (either 1, 2 or 3 OFDM symbols as defined by thePCFICH) within a sub-frame. The region occupied by the N_(symb) ^(PDCCH)in the time domain and the N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers in thefrequency domain is also referred to as PDCCH region or control channelregion. The remaining N_(symb) ^(PDCCH)=2·N_(symb)−N_(symb) ^(PDCCH)OFDM symbols in the time domain on the N_(RB) ^(DL)×N_(sc) ^(RB)subcarriers in the frequency domain is referred to as the PDSCH regionor shared channel region (see below).

For a downlink grant on the physical downlink shared channel (PDSCH),the PDCCH assigns a PDSCH resource for (user) data within the samesub-frame. The PDCCH control channel region within a sub-frame consistsof a set of CCE where the total number of CCEs in the control region ofsub-frame is distributed throughout time and frequency control resource.Multiple CCEs can be combined to effectively reduce the coding rate ofthe control channel. CCEs are combined in a predetermined manner using atree structure to achieve different coding rate.

In 3GPP LTE, a PDCCH can aggregate 1, 2, 4 or 8 CCEs. The number of CCEsavailable for control channel assignment is a function of severalfactors, including carrier bandwidth, number of transmit antennas,number of OFDM symbols used for control and the CCE size, etc. MultiplePDCCHs can be transmitted in a sub-frame.

On a transport channel level, the information transmitted via the PDCCHis also refereed as L1/L2 control signaling. L1/L2 control signaling istransmitted in the downlink for each user equipment (UE). The controlsignaling is commonly multiplexed with the downlink (user) data in asub-frame (assuming that the user allocation can change from sub-frameto sub-frame). Generally, it should be noted that user allocation mightalso be performed on a TTI (Transmission Time Interval) basis where theTTI length (in the time domain) is equivalent to either one or multiplesub-frames. The TTI length may be fixed in a service area for all users,may be different for different users, or may even by dynamic for eachuser. Generally, then the L1/L2 control signaling needs only betransmitted once per TTI.

Furthermore, the PDCCH information sent on the L1/L2 control signalingmay be separated into the Shared Control Information (SCI) and DedicatedControl Information (DCI).

The physical downlink shared channel (PDSCH) is mapped to the remainingOFDM symbols within one sub-frame that are not occupied by the PDCCH.The PDSCH resources are allocated to the user equipments in units ofresource blocks for each sub-frame.

FIG. 8 shows the exemplary mapping of PDCCH and PDSCH within a normalsub-frame (having 2·N_(symb)=14 OFDM symbols in the time domain),respectively a resource block pair (see magnification). The firstN_(symb) ^(PDCCH)=2 OFDM symbols (PDCCH region) are used for L1/L2control signaling, i.e. for signaling the PDCCH, and the remainingN_(symb) ^(PDCCH)=12 OFDM symbols (PDSCH region) are used for data.Within the resource block pairs of all sub-frames, cell-specificreference signals, CRS (Common Reference Signal), are transmitted. Thesecell-specific reference signals are transmitted on one or several ofantenna ports 0 to 3. In this example, the CRS are transmitted from twoantenna ports: R0 is from antenna port 0 and R1 is from antenna port 1.

Furthermore, the sub-frame also contains UE specific reference signals,DM-RS (DeModulation Reference Signal) that are used by the userequipments for demodulating the PDSCH. The DM-RS are only transmittedwithin the resource blocks where the PDSCH for a certain user equipmentis allocated. In order to support MIMO (Multiple Input Multiple Output)with DM-RS, four DM-RS layers are defined, which means at most MIMO offour layers is supported. In the example of FIG. 8, DM-RS layer 1, 2, 3,are 4 are corresponding to MIMO layer 1, 2, 3, and 4.

FIG. 9 shows another example where the PDCCH and the PDSCH is mapped toa MBSFN sub-frame. The example of FIG. 8 is quite similar to FIG. 8,except for the MBSFN sub-frame not comprising common reference signals.

For further information on the LTE physical channel structure indownlink and the PDSCH and PDCCH format, see St. Sesia et al., “LTE—TheUMTS Long Term Evolution”, Wiley & Sons Ltd., ISBN 978-0-47069716-0,April 2009, sections 6 and 9. Additional information on the use ofreference signals and channel estimation in 3GPP LTE can be found insection 8 of this book.

Further Advancements for LTE—LTE-Advanced (3GPP LTE-A)

The frequency spectrum for IMT-Advanced was decided at the World Radiocommunication Conference 2007 (WRC-07) in November 2008. Although theoverall frequency spectrum for IMT-Advanced was decided, the actualavailable frequency bandwidth is different according to each region orcountry. Following the decision on the available frequency spectrumoutline, however, standardization of a radio interface started in the3rd Generation Partnership Project (3GPP). At the 3GPP TSG RAN #39meeting, the Study Item description on “Further Advancements for E-UTRA(LTE-Advanced)” was approved which is also referred to as “Release 10”.The study item covers technology components to be considered for theevolution of E-UTRA, e.g. to fulfill the requirements on IMT-Advanced.Two major technology components which are currently under considerationfor LTE-A are described in the following.

In order to extend the overall system bandwidth, LTE-A (Release 10) usescarrier aggregation, where two or more component carriers as defined forLTE (Release 8)—see FIG. 1 and FIG. 2 discussed above—are aggregated inorder to support wider transmission bandwidths e.g. up to 100 MHz andfor spectrum aggregation. It is commonly assumed that a single componentcarrier does not exceed a bandwidth of 20 MHz.

A terminal may simultaneously receive and/or transmit on one or multiplecomponent carriers depending on its capabilities:

-   -   An LTE-Advanced (Release 10) compatible mobile terminal with        reception and/or transmission capabilities for carrier        aggregation can simultaneously receive and/or transmit on        multiple component carriers. There is one Transport Block (in        absence of spatial multiplexing) and one HARQ entity per        component carrier.    -   An LTE (Release 8) compatible mobile terminal can receive and        transmit on a single component carrier only, provided that the        structure of the component carrier follows the Release 8        specifications.

It is also envisioned to configure all component carriers LTE (Release8)-compatible, at least when the aggregated numbers of componentcarriers in the uplink and the downlink are same. Consideration ofnon-backward-compatible configurations of LTE-A (Release 10) componentcarriers is not precluded. Accordingly, it will be possible to configurea user equipment to aggregate a different number of component carriersof possibly different bandwidths in the uplink and the downlink.

Relaying Functionality—

Introduction of Relay Nodes to the UTRAN Architecture of 3GPP LTE-A

Relaying is considered for LTE-A as a tool to improve e.g. the coverageof high data rates, group mobility, temporary network deployment, thecell-edge throughput and/or to provide coverage in new areas.

The relay node is wirelessly connected to radio-access network via adonor cell. Depending on the relaying strategy, a relay node may be partof the donor cell or may control cells of its own. In case the relaynode is part of the donor cell, the relay node does not have a cellidentity of its own (but may still have a relay ID). In the case therelay node is in control of cells of its own, the relay node controlsone or several cells and a unique physical-layer cell identity isprovided in each of the cells controlled by the relay.

At least “Type 1” relay nodes will be part of 3GPP LTE-A. A “type 1”relay node is a relaying node characterized by the following:

-   -   The relay node controls cells, each of which appears to a user        equipment as a separate cell distinct from the donor cell.    -   The cells should have its own Physical Cell ID (defined in 3GPP        LTE (Release 8)) and the relay node shall transmit its own        synchronization channels, reference symbols, etc.    -   In the context of single-cell operation, the user equipment        should receive scheduling information and HARQ feedback directly        from the relay node and send its control channels (SR/CQI/ACK)        to the relay node    -   The relay node should appear as a 3GPP LTE-compliant eNodeB to        3GPP LTE-compliant user equipments (i.e. be backwards        compatible)    -   To 3GPP LTE-A-compliant user equipment, a “type 1” relay node        should appear differently than 3GPP LTE-compliant eNodeB to        allow for further performance enhancement.

An exemplary network structure using relay nodes in 3GPP LTE-A is shownin FIG. 3. The link between donor eNodeB (d-eNB) and relay node is alsoreferred to as relay backhaul link. The link between relay node and userequipments attached to the relay node (r-UEs) is called relay accesslink.

Propagation Delay Between Node B and Relay Node

In the following, a network configuration as shown in FIG. 3 is assumedfor exemplary purposes. The donor eNode B transmits L1/L2 control anddata to a so-called macro-user equipment (UE1) and also to a relay(relay node), and the relay node transmits L1/L2 control and data to aso-called relay-user equipment (UE2). Further assuming that the relaynode operates in a time-duplexing mode, i.e. transmission and receptionoperation are not performed at the same time, we arrive at anon-exhaustive entity behavior over time as shown in FIG. 4. Wheneverthe relay node is in “transmit” mode, UE2 needs to receive the L1/L2control channel and physical downlink shared channel (PDSCH), while whenthe relay node is in “receive” mode, i.e. it is receiving L1/L2 controlchannel and PDSCH from the Node B, it cannot transmit to UE2 andtherefore UE2 cannot receive any information from the relay node in sucha sub-frame.

The situation becomes somewhat trickier in case that the UE2 is notaware that it is attached to a relay node. As will be understood bythose skilled in the art, in a communication system without relay nodeany user equipment can always assume that at least the L1/L2 controlsignal is present in every sub-frame.

In order to support such a user equipment in operation beneath a relaynode, the relay node should therefore pretend such an expected behaviorin all sub-frames. This leads to a behavior as shown in FIG. 5. Therelay node has to transmit the L1/L2 control channel in each sub-frame(here assumed to be in the early part of each sub-frame), before it canswitch to reception mode. Additionally shown is a “Gap” which isrequired to tune the relay node hardware and software from “transmit” to“receive” mode and vice versa, which is typically a fraction of asub-frame. What can be seen is that effectively the time that isavailable for transmission from a Node B to a relay node is actuallyonly a fraction of a sub-frame, as indicated in the figure by the dashedbox. In 3GPP Release 8, the UE2 behavior shown for sub-frame 2, i.e. toreceive only the first part identical to the L1/L2 control signaling,can be achieved by configuring that sub-frame as an “MBSFN sub-frame”.Since this is done mainly to tell the UE2 to not process or expect theremainder of that sub-frame, it is also sometimes called a “fake MBSFNsub-frame”. In LTE, a node transmitting such “fake MBSFN” sub-frames isrequired to transmit the first two OFDM symbols of such a sub-framebefore it can switch to reception.

As shown in FIG. 6, it can be usually assumed that more than a singlerelay node is deployed and connected to a Node B. In addition, it ispossible that the relay node is not stationary, but can be mobile as auser equipment. For example, a relay node can be installed in a publictransportation vehicle such as a bus, train, or tramway. In any case,the distance between Node B and at least one relay node is variable, sothat different propagation delay for the signal from Node B to relaynodes will occur.

Using the exemplary deployment of FIG. 6, FIG. 7 illustrates thesituation assuming that the relay nodes' transmission is synchronized tothe Node B's transmission, as it is for example beneficial for the casethat a user equipment should easily hand over between the Node B and arelay node or for simultaneous multipoint transmission purposes. For thefirst two OFDM symbols of the fake MBSFN sub-frame, Node B, RN1, and RN2transmit simultaneously. Then for the relay nodes the first gap isrequired to switch to reception mode, followed by reception of the NodeB transmission signal until just before the end of the sub-frame, wherethe second gap is required by the relay nodes to switch back again totransmission mode before the beginning of the next sub-frame.

As can be seen, depending on the length of the gaps and propagationdelay for the signal between Node B and RN1 and between Node B and RN2,a relay node will be able to see only a limited and at least partiallydifferent set of OFDM symbols transmitted by the Node B. For RN1, thereception of OFDM symbol #1 overlaps with the gap, as does the receptionof OFDM symbol #12. For RN2, the reception of OFDM symbol #2 overlapswith the gap, as does the reception of OFDM symbol #13. While RN1 cansee OFDM symbols #2 to #11 completely, RN2 can see OFDM symbols #3 to#12 completely. Assuming a simple and cost-effective receiver at therelay node, partially invisible OFDM symbols cannot be used since theywould contain a lot of interference and should therefore be consideredas corrupt.

It may be thus assumed that the relay node is not able to detect theearly part of a sub-frame transmitted by a Node B, which usually carriesL1/L2 control information. Therefore, the Node B of transmitting to therelay node may use only those OFDM symbols within a R-PDCCH regionwithin a sub-frame for conveying the L1/L2 control information to therelay node that can be received by the relay node.

Relay Backhaul Sub-Frames

If the eNodeB-to-relay node link operates in the same frequency spectrumas the relay node-to-UE link, simultaneous eNodeB-to-relay node andrelay node-to-UE transmissions on the same frequency resource may not befeasible due to the relay transmitter causing interference to its ownreceiver, unless sufficient isolation of the outgoing and incomingsignals is provided. Therefore, when relay node transmits to donoreNodeB (d-eNB), it cannot receive signals from the user equipmentsattached to the relay node (r-UEs). Likewise, when relay node receivesfrom donor eNodeB (d-eNB), it cannot transmit to user equipmentsattached to the relay (r-UEs), as has been explained above with respectto FIG. 4 and FIG. 5.

Thus, there is sub-frame partitioning between relay backhaul link(eNodeB-to-relay node link) and relay access link (relay node-to-UElink). Currently it has been agreed that:

-   -   Relay backhaul downlink sub-frames, during which eNodeB to relay        node downlink backhaul transmission may occur, are        semi-statically assigned.    -   Relay backhaul uplink sub-frames, during which relay node to        eNodeB uplink backhaul transmission may occur, are        semi-statically assigned or implicitly derived by HARQ timing        from relay backhaul downlink sub-frames.

In relay backhaul downlink sub-frames, the relay node will transmit tothe donor eNodeB and r-UEs are not supposed to expect any relaytransmission. In order to support backward compatibility for r-UEs, therelay node configures the backhaul downlink sub-frames as MBSFNsub-frame. As shown in FIG. 5, the relay backhaul downlink sub-frameconsists of two parts. In the first OFDM symbols (up to two), the relaynode transmits to r-UEs as it would do for a normal MBSFN sub-frame. Inthe remaining part of the sub-frame, relay receives from donor eNodeB,so there is no relay node to r-UE transmission in this part of thesub-frame. r-UEs receive the first OFDM symbols (up to two) and ignorethe rest part of the sub-frame.

MBSFN sub-frame can be configured for every 10 ms and 40 ms. Hence,relay backhaul downlink sub-frames also support both 10 ms and 40 msconfiguration. Also similar to the MBSFN sub-frame configuration, relaybackhaul downlink sub-frames cannot be configured at sub-frames #0, #4,#5 and #9. Those sub-frames that are not allowed to be configured asbackhaul downlink sub-frames are called “illegal downlink sub-frames”here.

Relay downlink backhaul sub-frames can be normal sub-frames (asexemplified in FIG. 8) or MBSFN sub-frames (as exemplified in FIG. 9).

Relay Backhaul R-PDCCH Region

As outlined with respect to FIG. 5 and FIG. 7 above, the relay nodecannot receive L1/L2 control information (PDCCH) from donor eNodeBwithin the first OFDM symbols of the sub-frame. Thus, a new physicalcontrol channel (R-PDCCH) is used to dynamically or “semi-persistently”assign resources within the semi-statically assigned sub-frames to therelay node for the downlink and uplink backhaul data. The R-PDDCH(s) forthe relay node is/are mapped to a R-PDCCH region within the PDSCH regionof the sub-frame. The relay node expects to receive R-PDCCHs within thisregion of the sub-frame. In time domain, the R-PDCCH region spans theconfigured downlink backhaul sub-frames. In frequency domain, theR-PDCCH region exists on certain resource blocks that are configured forthe relay node by higher layer signaling.

R-PDCCH has following characteristics:

-   -   Within the physical resource blocks (PRBs) semi-statically        assigned for R-PDCCH transmission, a subset of the resources is        used for each R-PDCCH. The actual overall set of resources used        for R-PDCCH transmission within the above mentioned        semi-statically assigned PRBs may vary dynamically between        sub-frames.    -   These resources may correspond to the full set of OFDM symbols        available for the backhaul link or be constrained to a subset of        these OFDM symbols.    -   The resources that are not used for R-PDCCH within the above        mentioned semi-statically assigned PRBs may be used to carry        R-PDSCH or PDSCH.    -   The R-PDCCH is transmitted starting from an OFDM symbol within        the sub-frame that is late enough so that the relay can receive        it.    -   Both frequency distributed and frequency localized R-PDCCH        placement are supported.    -   Interleaving of R-PDCCHs within limited number of PRBs can have        diversity gain and at the same time limit the number of PRBs        that could be wasted.    -   In normal sub-frames, 3GPP LTE-A DM-RS (DeModulation Reference        Signal) is used when DM-RS are configured by eNodeB, otherwise        3GPP LTE CRS (Common Reference Signal) is used.    -   In MBSFN sub-frames, 3GPP LTE-A DM-RS is used.

The mapping of the R-PDCCH control information to the R-PDCCH regionwithin the PDSCH region of the backhaul downlink sub-frames is one ofthe topics discussed in 3GPP RAN1 working group.

SUMMARY OF THE INVENTION

One object of the invention is to suggest mapping of control informationfor a relay node to a control channel region defined for this relay nodewithin a sub-frame of an OFDM-based communication system. Another objectof the invention is to define a structure of this control channel regionthat allows for a distributed and localized mapping of controlinformation to the control channel region and/or that allows to minimizethe resources of the control channel region that need to be allocated toa user equipment.

The object is solved by the subject matter of the independent claims.Advantageous embodiments of the invention are subject to the dependentclaims.

A first aspect of the invention is to suggest a new organization of acontrol channel region that is to carry control information. Accordingto this aspect of the invention the control channel region is divided incontrol channel elements that have equal size irrespective of thepresence of further cell-specific and/or UE-specific reference signalswithin the control channel region. This is achieved by dividing thecontrol channel region in plural sub-control channel elements that arecombined to control channel elements all having equal size (in terms ofresource elements that can be used for the signaling of controlinformation, where a resource element is defined as one subcarrier inthe frequency domain and one ODFM symbol in the time domain).

The control channel region is divided in the frequency domain and/ortime domain in a FDM respectively TDM fashion in order to obtain thesub-control channel elements. For example, the OFDM symbols of thecontrol channel region may be divided into two groups, while in thefrequency domain the control channel region is divided every threesubcarriers. The resource elements of the respective blocks of threesubcarriers and the OFDM symbols of a respective one of the two groupsof OFDM symbols form the sub-control channel elements.

The control channel region may span plural resource block pairs of thesub-frame, and depending on the number of control channel elementsrequired for transmitting the control information to be signaled on thephysical resources of the control channel region and its mapping mode(localized or distributed), sub-control channel elements of the same ordifferent resource block pairs are combined to form the control channelelements. Furthermore, a distributed mapping of the control informationmay also be realized by mapping the control information to controlchannel elements of different resource block pairs, while each of thecontrol channel elements themselves are formed by sub-control channelelements of one resource block pair only.

As will become apparent from the following in more detail, theprinciples of this invention may be used for the signaling of physicalcontrol channel information from a base station (donor eNodeB) to relaynodes, from a base station (eNodeB) to mobile terminals (userequipments) and from a relay node to mobile terminals (user equipments).Accordingly, it will be referred to transmitting the control informationfrom a “transmitting apparatus” (i.e. base station or relay node) to a“receiving apparatus” (i.e. relay node or mobile terminal) herein.

According to one exemplary embodiment of the invention, a controlchannel region within a sub-frame of a 3GPP-based based communicationsystem using OFDM in the downlink is defined. The control channel regionconsists of at least two physical resource block pairs comprisingreference signals in a plurality of the resource elements of the atleast two physical resource block pairs. The physical resource blockpairs of the control channel region are divided into control channelelements in the following fashion: Each of the physical resource blockpairs of the control channel region is divided into a plurality ofdistinct sub-control channel elements by frequency division and/or timedivision (e.g. in a FDM, TDM or FDM/TDM fashion). The sub-controlchannel elements have different sizes and are combined to form controlchannel elements of equal size for conveying physical downlink controlchannel information.

In a further embodiment of the invention, the sub-control channelelements have either k₁ or k₂ resource elements for conveying thephysical downlink control channel information (i.e. not counting thereference symbols comprised in the respective sub-control channelelement). Each control channel element is formed by a combination of nsub-control channel element)s) having k₁ resource elements for conveyingthe physical downlink control channel information and n sub-controlchannel element)s) having k₂ resource elements for conveying thephysical downlink control channel information, where n is a naturalnumber (nε

and n>0). In one example, the control channel elements are formed bypairs of sub-control channel elements of size k₁ and k₂ resourceelements.

A further, more specific exemplary embodiment of the invention isdividing the control channel region in frequency and time domain inorder to obtain the sub-control channel elements, and pairs of thesub-control channel elements form respective control channel elements.Also in this exemplary embodiment, a control channel region within asub-frame of a 3GPP-based based communication system using OFDM in thedownlink is assumed. The control channel region spans N_(symb)^(R-PDCCH) OFDM symbols in the time domain and consists of at least twophysical resource block pairs. The resource block pairs comprisereference signals in a plurality of the resource elements and aredivided control channel elements for conveying physical downlink controlchannel information as follows: Each of the plural physical resourceblock pairs of the control channel region is divided into2·N_(SC)/N_(SC) ^(CCE) sub-control channel elements. N_(SC) ^(CCE)>1 andis denoting the number of subcarriers of each of the sub-control channelelements within the respective physical resource block pair.

The sub-control channel elements is divided into two groups: a firstgroup of the sub-control channel elements within a respective physicalresource block pair consists of N_(SC)/N_(SC) ^(CCE) of the sub-controlchannel elements and the sub-control channel elements of the first groupspan a first subset of said N_(symb) ^(R-PDCCH) OFDM symbols in the timedomain, and a second group of the sub-control channel elements within arespective physical resource block pair consists of the remainingN_(SC)/N_(SC) ^(CCE) of the sub-control channel elements and thesub-control channel elements of the second group span another, secondsubset of said N_(symb) ^(R-PDCCH) OFDM symbols in the time domain.Furthermore, respective control channel elements of equal size areformed by pairs of sub-control channel elements, each control channelelement consisting of a sub-control channel element of the first groupand a sub-control channel element of the second group.

(In this embodiment,

${{N_{SC}/N_{SC}^{CCE}} \cdot \frac{N_{RB}^{R - {PDCCH}}}{2}} = N_{CCE}$can be considered the target number of control channel elements withinthe control channel region, where N_(RB) ^(R-PDCCH) is the number ofresource blocks in the control channel region. N_(SC) ^(CCE) should bechosen so that equal number of subcarriers are contained in eachsub-control channel element, i.e. N_(SC) mod N_(SC) ^(CCE)=0)

In a more detailed exemplary embodiment, the sub-control channelelements in the first group have different numbers of resource elementsfor conveying the physical downlink control channel information (i.e.that can be used for carrying the control information and are notrequired for reference signals), and the sub-control channel elements inthe second group have different numbers of resource elements forconveying the physical downlink control channel information.

For example, the sub-control channel elements in the first group haveeither k₁ or k₂ resource elements for conveying the control information,and the sub-control channel elements in the second group have either l₁or l₂ resource elements for conveying the control information, whereink₁+l₂=k₂+l₁ and where k₁≠k₂ and l₁≠l₂.

In a further embodiment of the invention, that is applicable to acontrol channel region where sub-control channel elements are formed byfrequency division and/or time division, the sub-frame has two slots,each slot spanning N_(symb) OFDM symbols in the time domain. In thisembodiment of the invention, the sub-control channel elements spaneither N_(symb)−N_(symb) ^(PDCCH) OFDM symbols in the first slot of thesub-frame in the time domain, or the N_(symb) OFDM symbols of the secondslot of the sub-frame in the time domain, where N_(symb) ^(PDCCH) ε[0, .. . , 4] and N_(symb) ^(PDCCH)<N_(symb).

The number N_(symb) ^(PDCCH) may be for configured on a dynamic basis(e.g. corresponding to the PCFICH value signaled in each sub-frame),semi-static basis (e.g. configured by radio resource control signalingor by means of system information broadcast) or static basis (e.g.predefined).

In one further exemplary embodiment of the invention, it is exemplarilyassumed that the first N_(symb) ^(PDCCH) ε[0, . . . , 4] OFDM symbols ofeach sub-frame is defining a physical downlink control channel region(PDCCH region), while the remaining OFDM symbols of the sub-frame aredefining a shared data region (or physical downlink shared channel(PDSCH) region). In this scenario, the control channel region may be forexample located in a PDSCH region of the sub-frame.

Alternatively, in another embodiment of the invention, the sub-framesmay not comprise a PDCCH region, but the time-frequency resources of thesub-frame can be dedicated for control signaling or transmission of userdata on a dynamic basis or semi-static basis. In this example, atransmitting apparatus may configure a control channel region forrespective receiving apparatuses in which the respective receivingapparatuses can expect to receive its control signaling. For example,the control channel regions may overlap or may be identical for some orall receiving apparatuses.

In a further exemplary embodiment, the sub-control channel elements ofeach pair of sub-control channel elements forming a control channelelement may be located on different subcarriers.

Furthermore, in some embodiments of the invention, the sub-controlchannel elements each comprise at least one resource element used forsending a demodulation reference signal and/or a common referencesignal.

Other embodiments of the invention provide a method for mapping physicaldownlink control channel information for a receiving apparatus tocontrol channel elements of a control channel region of a sub-frame of a3GPP-based based communication system using OFDM in the downlink.According to one exemplary embodiment, the transmitting apparatusassigns to a receiving apparatus a control channel region withinsub-frames for signaling control information to the receiving apparatus.The assigned control channel region is spanning plural physical resourceblock pairs consisting each of a plurality of N_(SC) subcarriers in thefrequency domain and N_(symb) ^(R-PDCCH) OFDM symbols in the timedomain. The control channel region has a structure according to one ofthe different embodiments of the invention described herein.Furthermore, the transmitting apparatus maps the physical downlinkcontrol channel information for the receiving apparatus to the controlchannel elements defined in the control channel region.

In one more detailed, exemplary implementation the physical downlinkcontrol channel information is mapped to 2^(i) of the control channelelements defined in the control channel region, wherein iε{0,1,2,3, . .. }. Please note that 2^(i) should be smaller or equal to the number ofcontrol channel elements available. In one example, iε{0,1,2,3}, inanother example, iε{0,1,2,3,4}.

As mentioned already above, the principles of the invention facilitate alocalized and distributed mapping of the physical downlink controlchannel information to the control channel region. Basically, thelocalized mapping ensures that the control channel elements, to whichthe physical downlink control channel information is mapped, are withinone of the resource block pairs. If more control channel elements thanavailable in a single resource block pair are required for the physicaldownlink control channel information, the physical downlink controlchannel information is mapped to control channel elements of multiplephysical resource block pairs. The multiple physical resource blockpairs may be located adjacent to each other in the frequency domain, butmay also be distributed the frequency domain. In a distributed mappingthe physical downlink control channel information is mapped to controlchannel elements of non-adjacent physical resource block pairs.

In one exemplary implementation, in case the physical downlink controlchannel information is to be mapped to one control channel element andin case of using a localized mapping scheme for mapping the physicaldownlink control channel information to the one control channel element,the pair of sub-control channel elements forming the one control channelelement are located in one of the resource blocks of the control channelregion. In case the control information is to be mapped to one controlchannel element and in case of using a distributed mapping scheme formapping the physical downlink control channel information to the onecontrol channel element, the respective sub-control channel elements ofsaid pair of sub-control elements forming the control channel elementsare located in different resource blocks of the control channel region.

In another exemplary implementation, in case the control information isto be mapped to more than one control channel element and in case ofusing a localized mapping scheme for mapping the physical downlinkcontrol channel information to the control channel elements, therespective pairs of sub-control channel elements forming the controlchannel elements are located in one of the physical resource block pairsof the control channel region.

In case the control information is to be mapped to more than one controlchannel element and in case of using a distributed mapping scheme formapping the physical downlink control channel information to the onecontrol channel element:

-   -   the respective control channel elements to which the physical        downlink control channel information of the receiving apparatus        is mapped are located in different physical resource block        pairs, or    -   the control channel elements to which the physical downlink        control channel information of the receiving apparatus is mapped        are respectively formed by sub-control channel elements located        in different physical resource block pairs.

According to another exemplary embodiment, the transmitting apparatusgenerates a sub-frame comprising the physical downlink control channelinformation for the receiving apparatus mapped to the control channelregion and transmitting the sub-frame to the receiving apparatus.

In some embodiments of the invention, the receiving apparatus may useblind detection of the physical downlink control channel information. Inorder to address the physical downlink control channel information to areceiving apparatus, the transmitting apparatus determines a CRC codefor the physical downlink control channel information for the receivingapparatus, and masks the CRC code with a receiving apparatus-specificidentifier. The transmitting apparatus further appends the masked CRCcode to the physical downlink control channel information for thereceiving apparatus within a CRC field. The transmitting apparatusfurther maps the coded physical downlink control channel information forthe receiving apparatus to one or more control channel elements of thecontrol channel region together with the CRC field comprising the maskedCRC code.

Other embodiments of the invention relate to the definition of thecontrol channel region (i.e. the physical resources within the sub-framethat span same). The physical resource block pairs for signaling thephysical control channel information to the receiving apparatus may be:

-   -   configured by the transmitting apparatus by means of radio        resource control signaling,    -   configured by the transmitting apparatus by means of system        information broadcast in the radio cell of the transmitting        apparatus, and/or    -   pre-determined (e.g. as part of a standardization document).

In one exemplary implementation, the transmitting apparatus is signalingto the receiving apparatus a control channel assignment message forconfigures the one or more physical resource block pairs for signalingthe control channel region to the receiving apparatus. The controlchannel assignment message may be a Radio Resource Control message or anInformation Element of a Radio Resource Control message. In anotherembodiment of the invention, the transmitting apparatus broadcastssystem information comprising a control channel assignment forconfiguring the one or more physical resource block pairs for signalingthe control channel region to the receiving apparatus.

The control channel assignment message configures the physical resourceblock pairs for signaling the physical control channel information tothe receiving apparatus on a semi-static basis or on a dynamic basis.Furthermore, if the control channel region is not to span apredetermined region in the time domain (e.g. up to a slot boundary inthe sub-frame, entire shared data region within the sub-frame, etc.),the control channel assignment message may also indicate the OFDMsymbols that belong to the control channel region (for example bysending a start index and/or end index of the OFDM symbol(s) that definethe start/end of the control channel region in the time domain).

Furthermore, it is also possible that the same control channel region orpartly overlapping control channel regions is/are assigned to pluralreceiving apparatuses, including the receiving apparatus.

In one further exemplary embodiment of the invention, the transmittingapparatus may modulate the information of the control channel element(s)conveying the physical downlink control channel information for thereceiving apparatus using a pre-determined modulation and coding scheme.

Further embodiments of the invention relate to a method for receivingcontrol information for a receiving apparatus of a 3GPP-basedcommunication system using OFDM in the downlink, where a receivingapparatus receives a sub-frame from a transmitting apparatus, whereinthe sub-frame comprises a control channel region structured according toone of the different embodiments described herein. The control channelregion in the sub-frame is divided into plural control channel elementsfor conveying physical downlink control channel information to thereceiving apparatus. The receiving apparatus obtains the physicaldownlink control channel information for the receiving apparatus fromthe control channel elements comprised in the sub-frame.

Furthermore, in another embodiment of the invention the receivingapparatus is performing within the control channel region of thereceiving apparatus, a blind detection of physical downlink controlchannel information comprised in one or more of the control channelelements.

The receiving apparatus may obtain a masked CRC code from a CRC fieldwithin the control channel element(s) conveying the physical downlinkcontrol channel information, de-mask the masked CRC code with areceiving apparatus-specific temporary identifier, and verifyingsuccessful blind detection of the control information for the receivingapparatus based on the CRC code.

Moreover, the receiving apparatus may also receiving from a transmittingapparatus a control channel assignment message for configures thephysical resource block pairs for signaling the physical downlinkcontrol channel information to the receiving apparatus.

Other embodiments of the invention relate to the implementation of theprinciples of this invention in hardware and/or software. Accordingly,another embodiment of the invention is providing a transmittingapparatus for use in a 3GPP-based based communication system using OFDMin the downlink. The transmitting apparatus is capable of mappingcontrol channel information for a receiving apparatus to control channelelements of a control channel region of a sub-frame. The transmittingapparatus comprises a processing unit for assigning to a receivingapparatus a control channel region within sub-frames for signalingphysical downlink control channel information to the receivingapparatus. The assigned control channel region is thereby spanning oneor more physical resource block pairs consisting each of a plurality ofN_(SC) subcarriers in the frequency domain and N_(symb) ^(R-PDCCH) OFDMsymbols in the time domain. Furthermore, the control channel region isstructured according to one of the different embodiments describedherein. The transmitting apparatus also comprises a mapping unit formapping the physical downlink control channel information for thereceiving apparatus to the control channel elements defined in thecontrol channel region.

The transmitting apparatus according to another embodiment of theinvention comprises a transceiver unit for signaling to the receivingapparatus a control channel assignment message for assigning thephysical resource block pairs for signaling the physical downlinkcontrol channel information to the receiving apparatus.

In a further embodiment of the invention, the transmitting apparatus'sprocessing unit is adapted to generate a sub-frame comprising thephysical downlink control channel information for the receivingapparatus in the control channel region, wherein the control channelregion for the receiving apparatus is located in the shared data regionof the sub-frame. Moreover, the transceiver unit of the transmittingapparatus is adapted to transmit the sub-frame to the receivingapparatus.

The transmitting apparatus according to another embodiment of theinvention is comprising means adapted to perform the steps of the formapping physical downlink control channel information for a receivingapparatus to control channel elements of a control channel region of asub-frame of a 3GPP-based based communication system using OFDM in thedownlink according to one of the various exemplary embodiments describedherein.

Another embodiment of the invention is related to a receiving apparatusfor receiving control information for a receiving apparatus of a3GPP-based communication system using OFDM in the downlink. Thereceiving apparatus comprises a receiver unit for receiving a sub-framefrom a transmitting apparatus, wherein the sub-frame comprises a controlchannel region structured according to one of the various embodimentsdescribed herein. The control channel region is further divided intoplural control channel elements for conveying physical downlink controlchannel information to the receiving apparatus. The receiving apparatusfurther has a processing unit obtaining from the control channelelements comprised in the sub-frame the physical downlink controlchannel information for the receiving apparatus.

In another embodiment of the invention, the processing unit of thereceiving apparatus is adapted to perform within the control channelregion of the receiving apparatus, a blind detection of physicaldownlink control channel information comprised in one or more of thecontrol channel elements.

The processing unit of the receiving apparatus is for example adapted toobtain a masked CRC code from a CRC field within the control channelelement(s) conveying the coded physical downlink control channelinformation, to de-mask the masked CRC code with a receivingapparatus-specific temporary identifier, and to verify successful blinddetection of the physical downlink control channel information for thereceiving apparatus based on the CRC code.

Moreover, according to another embodiment, the receiving apparatus alsocomprises a receiver unit for receiving from a transmitting apparatus acontrol channel assignment message for configures the physical resourceblock pairs for signaling the physical downlink control channelinformation to the receiving apparatus.

Another embodiment of the invention is providing a computer-readablemedium that is storing instructions that. when executed by a processingunit of a transmitting apparatus, cause the transmitting apparatus toperform the method for mapping physical downlink control channelinformation for a receiving apparatus to control channel elements of acontrol channel region of a sub-frame of a 3GPP-based basedcommunication system using OFDM in the downlink according to one of thevarious embodiment of the invention described herein. The executedinstructions may cause the transmitting apparatus to assign to areceiving apparatus a control channel region within sub-frames forsignaling control information to the receiving apparatus. The assignedcontrol channel region is spanning plural physical resource block pairsconsisting each of a plurality of N_(SC) subcarriers in the frequencydomain and N_(symb) ^(R-PDCCH) OFDM symbols in the time domain. Thecontrol channel region has a structure according to one of the differentembodiments of the invention described herein. Furthermore, thetransmitting apparatus may be caused by the execution of theinstructions to map the physical downlink control channel informationfor the receiving apparatus to the control channel elements defined inthe control channel region.

Another embodiment of the invention is providing a computer-readablemedium that is storing instructions that. when executed by a processingunit of a receiving apparatus, cause the transmitting apparatus toperform the method for mapping physical downlink control channelinformation for a receiving apparatus to control channel elements of acontrol channel region of a sub-frame of a 3GPP-based basedcommunication system using OFDM in the downlink according to one of thevarious embodiment of the invention described herein.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows the general structure of a sub-frame on a downlinkcomponent carrier as defined for 3GPP LTE (Release 8),

FIG. 2 shows an exemplary downlink resource grid of one of the twodownlink slots of a sub-frame as defined for 3GPP LTE (Release 8),

FIG. 3 shows an exemplary network configuration of a donor eNodeB(d-eNB), a relay node (RN) and two user equipments (UE1 and UE2),

FIG. 4 shows an exemplary behavior of the entities in FIG. 3 withrespect to their operation in transmission mode and reception mode,

FIG. 5 shows an exemplary backward-compatible behavior of the entitiesin FIG. 3 with respect to their operation in transmission mode andreception mode in an enhanced communication system, such as 3GPP LTE-A(Release 10),

FIG. 6 shows another exemplary network configuration of a donor eNodeB(d-eNB), multiple relay nodes (RN1 and RN2) and multiple userequipments,

FIG. 7 exemplarily illustrates the reception of a sub-frame from a donoreNodeB at different relay nodes and the transmission windows andreception windows of the relay nodes, taking into account the variablepropagation delay of transmission signals between the donor eNodeB(d-eNB) and relay nodes (RN1 and RN2) and a switching betweentransmission mode and reception mode within the sub-frame at the relaynodes,

FIGS. 8 & 9 exemplify the structure of a normal sub-frames, respectivelya MBSFN sub-frames and a physical resource block pair thereof as definedfor 3GPP LTE (Release 8) and 3GPP LTE-A (Release 10) and as used in someof the embodiments of the invention,

FIG. 10 exemplifies a division of two physical resource block pairs #mand #n of a R-PDCCH region into eight control channel elements (CCEs),

FIG. 11 exemplifies a division of two physical resource block pairs #mand #n of a R-PDCCH region of a normal sub-frame into sixteensub-control channel elements (sub-CCEs) according to an exemplaryembodiment of the invention,

FIGS. 12 & 13 show exemplary combinations of pairs of sub-controlchannel elements (sub-CCEs) of FIG. 11 to form eight control channelelements (CCEs) that allow for a localized, respectively distributedmapping of the R-PDCCH information according to an embodiment of theinvention,

FIG. 14 shows an exemplary combination of pairs of sub-control channelelements (sub-CCEs) of FIG. 11 to form eight control channel elements(CCEs) that allow for a localized and distributed mapping of the R-PDCCHinformation according to an embodiment of the invention,

FIG. 15 exemplifies another division of two physical resource blockpairs #m and #n of a R-PDCCH region into sixteen sub-control channelelements (sub-CCEs) according to an exemplary embodiment of theinvention,

FIG. 16 shows another exemplary combination of pairs of sub-controlchannel elements (sub-CCEs) of FIG. 15 to form eight control channelelements (CCEs) that allow for a localized mapping of the R-PDCCHinformation according to an embodiment of the invention,

FIG. 17 exemplifies a division of two physical resource block pairs #mand #n of a R-PDCCH region of a MBSFN sub-frame into sub-control channelelements (sub-CCEs) according to an exemplary embodiment of theinvention,

FIG. 18 exemplifies another division of two physical resource blockpairs #m and #n of a R-PDCCH region into eight sub-control channelelements (sub-CCEs) according to an exemplary embodiment of theinvention,

FIGS. 19 & 20 shows exemplary combinations of pairs of sub-controlchannel elements (sub-CCEs) of FIG. 18 to form four control channelelements (CCEs) using a localized, respectively distributed,

FIGS. 21 & 22 show exemplary combinations of pairs of sub-controlchannel elements (sub-CCEs) of FIG. 11 to form four control channelelements (CCEs) using a localized, respectively distributed mapping ofthe R-PDCCH information according to an embodiment of the invention,

FIG. 23 exemplifies a further division of two physical resource blockpairs #m and #n of a R-PDCCH region of a normal sub-frame into 8sub-control channel elements (sub-CCEs) according to an exemplaryembodiment of the invention,

FIGS. 24 & 25 show exemplary combinations of pairs of sub-controlchannel elements (sub-CCEs) of FIG. 23 to form four control channelelements (CCEs) using a localized, respectively distributed mapping ofthe R-PDCCH information according to an embodiment of the invention, and

FIGS. 26 to 29 show different exemplary configuration of a controlchannel region within a sub-frame according to different embodiments ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to an orthogonal single-carrier uplink radio accessscheme according to 3GPP LTE (Release 8) and LTE-A (Release 10) mobilecommunication systems discussed in the Technical Background sectionabove. It should be noted that the invention may be advantageously usedfor example in connection with a mobile communication system such as3GPP LTE (Release 8) and LTE-A (Release 10) communication systemspreviously described, but the invention is not limited to its use inthis particular exemplary communication network.

The explanations given in the Technical Background section above areintended to better understand the mostly 3GPP LTE (Release 8) and LTE-A(Release 10) specific exemplary embodiments described herein and shouldnot be understood as limiting the invention to the described specificimplementations of processes and functions in the mobile communicationnetwork.

One solution for the mapping of the control information for a relay nodeto its control channel region within the shared data region of thebackhaul downlink sub-frames is to divide each physical resource blockpair into several control channel elements as exemplified in FIG. 10.FIG. 10 shows an exemplary division of two physical resource block pairs#m and #n that are considered to be part of a R-PDCCH region of a relaynode into 8 control channel elements (CCEs). Please note that FIG. 10further assumes that normal sub-frames, as exemplified in FIG. 8 areemployed on the downlink between donor eNodeB and relay node within a3GPP-LTE or LTE-A compatible communication network.

The R-PDCCH information is mapped to a limited number of physicalresource block pairs. In the exemplary division of the physical resourceblock pair of FIG. 10, CCE level interleaving among of R-PDCCHinformation of different relay nodes that have overlapping or identicalR-PDCCH regions can be used. Depending on whether the two physicalresource block pairs are localized (e.g. n=m+1) or distributed (e.g.n=m+offset with offset >1) in frequency domain, localized or distributedmapping of R-PDCCH information for a relay node can be realized. Theoffset may be considered to correspond to a certain number ofsubcarriers, i.e. a given offset bandwidth. In one exemplary embodiment,the offset is chosen to be larger than or equal to the coherencebandwidth of the channel, such that the channel conditions within thesetwo resource blocks are independent.

In the example of FIG. 10, it is assumed that 8 CCEs should be availablein the two physical resource block pairs, so that in the frequencydomain the 2·N_(SC)=24 subcarriers of the two resource block pairs #mand #n are divided in blocks of N_(SC) ^(CCE)=24/8=3 subcarriers intothe CCEs. Due to the sub-frame structure of a normal sub-framecomprising cell-specific reference signals (e.g. CRS) and UE-specificreference signals (or for a relay node relay node-specific referencesignals), (e.g. DM-RS) as shown in FIG. 8, the resulting CCE havedifferent numbers of resource elements within each CCE being availablefor the signaling of the R-PDCCH information of a relay node. Table 1shows an overview of the number of resource elements per CCE in theexample shown in FIG. 10.

TABLE 1 Number of RE Number Number CCE for R-PDCCH of RE of RE numberinformation for CRS for DM-RS 1 22 3 8 2 26 3 4 3 26 3 4 4 22 3 8 5 22 38 6 26 3 4 7 26 3 4 8 22 3 8

As can be seen from Table 1 the amount of R-PDCCH information that canbe conveyed in the respective CCEs is differing among the CCEs (each REcorresponds to one modulation symbol and thus to a corresponding numberof coded bits depending on the modulation scheme level). This appearsnot desirable as this would either require the adaption of themodulation and coding rate to the number of REs available for R-PDCCHinformation so as to be able to convey an equal size of R-PDCCHinformation in each CCE (one can assume that the modulation scheme isfixed, while the code rate would need to be adapted). This howeverrequires a more complicated receiver side processing (as the appliedcode rate depends on the number of resource elements used for theR-PDCCH in the given CCE(s)). Furthermore, this would also require amore complicated R-PDCCH information-to-CCE mapping at the transmittingapparatus, since the required code rate for achieving a certain blockerror rate (BLER) or better, depends on the CCE number. For example, incase a R-PDCCH information is mapped to CCE #2 (26 REs), a CCEaggregation level of 1 may be sufficient, while in case a R-PDCCHinformation is mapped on CCE #1 (22 REs), a CCE aggregation level of 2may be required. Alternatively, different DCI formats of the R-PDCCHinformation may need to be defined so as to address the number of REsavailable for R-PDCCH information within the respective CCE(s) to whichthe R-PDCCH information is to be mapped. This latter option appears evenmore undesirable, since this would require a very complex interaction ofthe physical resource mapping functionality and coding functionality ofthe eNodeB.

Another solution and in accordance with a first aspect of the invention,a new organization of a control channel region for conveying controlinformation, such as physical downlink control channel (PDCCH)information is suggested. A control channel region is defined/configuredwithin sub-frames of a OFDM-based air interface of a mobilecommunications system, such as for example a 3GPP-based system like 3GPPLTE (Release 8) or LTE-A (Release 10). The control channel region isdivided into control channel elements that have equal size irrespectiveof the presence of further cell-specific and/or UE-specific referencesignals within the control channel region. This is achieved by dividingthe control channel region in plural sub-control channel elements. Thesub-channel elements are combined to control channel elements havingequal size. According to the first aspect of the invention, the controlchannel region is divided in the frequency domain and/or time domain ina FDM respectively TDM fashion.

“Equal in size” means that the number of resource elements available forthe signaling of control information within the control channel elementsis the same for all control channel elements of the control channelregion. It is a matter of definition whether the reference signals thatare located within the control channel elements are counted as part ofthe control channel elements or not, and the invention is applicable toboth options. In the following examples, the reference symbols are notpart of the sub-control channel elements and control channel elementsfor exemplary purposes only.

The control channel region may span plural resource block pairs of thesub-frame, but may not necessarily “cover” the entire time domainresources of the sub-frame. Depending on the number of control channelelements in the control channel region required for transmitting thecontrol information to be signaled on the physical resources of thecontrol channel region and its mapping mode (localized or distributed),sub-control channel elements of the same or different resource blockpairs are combined to form the control channel elements. Furthermore, adistributed mapping of the control information may also be realized bymapping the control information to control channel elements of differentresource block pairs, while each of the control channel elementsthemselves are formed by sub-control channel elements of one resourceblock pair only.

As will become apparent from the following in more detail, theprinciples of this invention may be used for the signaling of physicalcontrol channel information from a base station (donor eNodeB) to relaynodes, from a base station (eNodeB) to mobile terminals (userequipments) and from a relay node to mobile terminals (user equipments).Accordingly, it will be referred to transmitting the control informationfrom a “transmitting apparatus” (i.e. base station or relay node) to a“receiving apparatus” (i.e. relay node or mobile terminal) herein.

FIG. 26 to FIG. 29 show different exemplary configuration of a controlchannel region within a sub-frame according to different embodiments ofthe invention. Please note that in all four examples, the sub-framecontains reference signals in some of the resource elements of thesub-frame. The reference signals may be provided in a regular pattern.Furthermore, the reference signals may be for example common referencesignals (pertaining to all terminals/relay nodes of a radio cell),and/or terminal-specific reference signals, such as for example DM-RSfor respective user equipments/relay nodes. Please note that althoughthe FIG. 26 to FIG. 29 exemplarily indicate the physical resource blockpairs forming the control channel region to be adjacent to each other,this is not mandatory, but the individual resource block pairs may alsobe distributed in the frequency domain of the system bandwidth.Furthermore, it is also possible that there are adjacent andnon-adjacent physical resource block pairs configured as the controlchannel region.

FIG. 26 shows an example where the control region is configured withinthe shared data region (PDSCH region) of the sub-frame. This example maybe especially applicable (but not restricted to) for the transmission ofPDCCH information to relay nodes. The control channel region shown inFIG. 26 spans the entire N_(symb) ^(PDSCH) OFDM symbols of the PDSCHregion, i.e. N_(symb) ^(R-PDCCH)=N_(symb) ^(PDSCH)=2·N_(symb)−N_(symb)^(PDCCH) in this example, where N_(symb) ^(R-PDCCH) is the number ofOFDM symbols of the control region in the time domain, N_(symb) ^(PDSCH)is the number of OFDM symbols of the shared data region in the timedomain, N_(symb) ^(PDCCH) is the number of OFDM symbols of the controlchannel region (PDCCH region) in the time domain, and N_(symb) is thenumber of ODFM symbols of a respective one of the two slots of thesub-frame in the time domain.

Generally, N_(symb) ^(PDCCH) may be for example dynamically configured,e.g. may correspond to the PCFICH value that is signaled within asub-frame. Alternatively, N_(symb) ^(PDCCH) may be configured on asemi-static or static basis as well.

FIG. 27 shows another example where the control region is configuredwithin the shared data region (PDSCH region) of the sub-frame. In theexample shown in FIG. 27, the control channel region is not spanning theentire PDSCH region, but the control channel spans the OFDM symbols ofthe sub-frame starting at symbol index n_(start) ^(R-PDCCH). In theexample of FIG. 27, the N_(symb) ^(PDCCH) symbols of the control regionare the 5^(th) to the last (14^(th)) OFDM symbol of the sub-frame(n_(start) ^(R-PDCCH)=5). n_(start) ^(R-PDCCH) may be for exampleconfigured on a semi-static basis using RRC signaling or is broadcast inthe cell by means of system information. Alternatively, n_(start)^(R-PDCCH) could be static/predefined.

Please note that in a variation of this example, not only the startindex n_(start) ^(R-PDCCH) of the control region may be configured butalso the end index n_(end) ^(R-PDCCH), so that in the time domain thecontrol channel region spans the OFDM symbols n_(start) ^(R-PDCCH) ton_(end) ^(R-PDCCH) (n_(start) ^(R-PDCCH)<n_(end) ^(R-PDCCH)). Bothindices may be semi-statically or statically configured as describedabove.

The exemplary control channel configurations shown in FIG. 26 and FIG.27 may be useful for conveying physical downlink control channelinformation (e.g. uplink and downlink grants) to from a base station(donor eNodeB) to a relay node. However, as outlined above, theinvention is not limited to this scenario. FIG. 28 shows anotherexemplary configuration of a control channel region within a sub-frameaccording to another embodiment of the invention. In this example, thesub-frame has no control channel region configured, so that all OFDMsymbols of the sub-frame may be considered part of the PDSCH region. Inthis case the transmitting apparatus (donor eNodeB or relay node) mayconfigure control channel regions for the served receiving apparatus(es)(relay nodes or user equipments) that span the entire sub-frame in thetime domain (e.g. all 2·N_(symb) OFDM symbols of the sub-frame).

Alternatively, as shown in FIG. 29, the control channel region may alsobe configured to span only a certain range within the sub-frame, forexample the first or second slot thereof. Hence, the individual extendof the control channel region may also be limited by the slot boundarieswithin the sub-frame.

Also the control channel region configurations in FIG. 28 and FIG. 29may be configured on a dynamic, semi-static or static basis as outlinedabove. For example, for a semi-static configuration the starting indexn_(start) ^(R-PDCCH) and optionally the end index n_(end) ^(R-PDCCH) maybe configured.

In the following, control channel structures according to severalexemplary embodiments of the invention will be outlined. The embodimentsare given with respect to a 3GPP-based mobile communications networkusing OFDMA in the downlink. Furthermore, the control channel region isreferred to as R-PDCCH region in most of the examples below, as it isexemplarily assumed that the control channel structures discussed in thefollowing is used for providing PDCCH information for a relay node froma donor eNodeB to a relay node.

Moreover, the examples are based on the sub-frame structure of a 3GPPLTE (Release 8) system as shown in FIG. 8 and FIG. 9. When applying thisinvention to 3GPP LTE-A (Release 10), it can be assumed that thesub-frame structure of 3GPP LTE (Release 8) is reused on the aggregatedcomponent carriers. In this case the sub-frame will span the aggregatedcomponent carriers of a user equipment, respectively relay node, i.e.the total number N_(RB) ^(DL) of downlink resource blocks availablewithin the sub-frame accounts for the total bandwidth of the aggregatedcomponent carriers. Though the sub-frame may span the entire bandwidth othe aggregated component carriers, the control channel region may stillbe defined per-component carrier. Also resource allocation by means ofphysical downlink control channel information may be performed for theindividual component carriers rather than one aggregated componentcarrier. The use of sub-frame structures of a 3GPP LTE (Release 8)system is only exemplary and not limiting the invention to thesestructures.

FIG. 11 exemplifies a division of two physical resource block pairs #mand #n of a R-PDCCH region of a normal sub-frame into 16 sub-controlchannel elements (sub-CCEs) according to an exemplary embodiment of theinvention. In FIG. 11, the approach depicted in FIG. 26 is adopted, i.e.the control channel region is spanning the PDSCH region of thesub-frame. Furthermore, the sub-frame is assumed to have a PDCCH regionthat is spanning the first two OFDM symbols—please note that the PDCCHregion of the sub-frame may have N_(symb) ^(PDCCH)ε[0, . . . , 4] OFDMsymbols in the time domain.

The R-PDCCH channel region is spanning N_(RB) ^(R-PDCCH) resource blocksin the frequency domain and N_(symb) ^(R-PDCCH) OFDM symbols in the timedomain. Please note that the control channel region may span multipleresource blocks (even and odd numbers) in the frequency domain. FIG. 11exemplarily depicts the organization of sub-control channel elements fortwo physical resource block pairs. If there are more than two resourceblock pairs configured from the R-PDCCH region, the other resource blockpairs are divided into sub-control channel elements in a similar fashionas shown in FIG. 11.

The R-PDCCH region of the exemplary embodiment of FIG. 11 is divided inthe time domain into two groups of OFDM symbols (first group and secondgroup). In the frequency domain, the N_(SC)=12 subcarriers per resourceblock is divided into blocks of N_(SC) ^(CCE)=3 subcarriers so thatthere are N_(SC)/N_(SC) ^(CCE)=4 subcarriers comprised in eachsub-control element. Although also other values may be chosen for N_(SC)^(CCE) as long as N_(SC) mod N_(SC) ^(CCE)=0, the value N_(SC) ^(CCE)=3together with the division of the R-PDCCH region in the time domainappears of particular advantage in connection with the assumed sub-framestructure of FIG. 8 and FIG. 9, as the proposed division of the R-PDCCHregion into sub-control channel elements (sub-CCE #i) allows for havingeither two resource elements or four resource elements per sub-controlchannel element, which allows a simple combination of pairs ofsub-control channel elements to control channel elements of equal size.

Furthermore, it should be noted in FIG. 11 that the boundary of thesub-control channel elements is defined by the slot boundaries of thesub-frame. Hence the first group of sub-control channel elements isspanning the N_(symb)−N_(symb) ^(PDCCH)=5 OFDM symbols, while thecontrol channel elements of the second group is spanning the remainingN_(symb)=7 OFDM symbols, i.e. the second slot of the sub-frame in thetime domain.

The sub-control channel elements in the first group have either k₁=10 ork₂=12 resource elements for conveying the control information, i.e.which are not used for reference signals. The sub-control channelelements in the second group have either l₁=15 or l₂=17 resourceelements for conveying the control information. Thus, the sub-controlchannel elements #1 to #8 can be combined respectively with one ofsub-control channel elements #9 to #16 to form control channel elementsof size j=k₁+l₂=k₂+l₁=27 (i.e. 27 resource elements are available toconvey the PDCCH information for the receiving apparatus).

FIG. 12 and FIG. 13 show exemplary combinations of pairs of the 16sub-control channel elements (sub-CCEs) of FIG. 11 to form 8 controlchannel elements (CCEs) using a localized, respectively distributedmapping of the R-PDCCH information according to an embodiment of theinvention. FIG. 2 and Table 2 show the combination of sub-controlchannel elements to obtain a localized mapping of control channelelements.

TABLE 2 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #10 PRB pair #m CCE #2 Sub-CCE #2Sub-CCE #9 PRB pair #m CCE #3 Sub-CCE #3 Sub-CCE #12 PRB pair #m CCE #4Sub-CCE #4 Sub-CCE #11 PRB pair #m CCE #5 Sub-CCE #5 Sub-CCE #14 PRBpair #n CCE #6 Sub-CCE #6 Sub-CCE #13 PRB pair #n CCE #7 Sub-CCE #7Sub-CCE #16 PRB pair #n CCE #8 Sub-CCE #8 Sub-CCE #15 PRB pair #n

As can be seen from Table 2 and FIG. 12, all control channel elementsare defined within one of the physical resource block pairs of theR-PDCCH region. Accordingly, also in case of using more then twophysical resource block pairs such control channel elements of equalsize can be built within a respective physical resource block pair.

Table 3 below shows an alternative combination of sub-control channelelements shown in FIG. 11 to form control channel elements that allowfor a localized mapping of the PDCCH information.

TABLE 3 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #11 PRB pair #m CCE #2 Sub-CCE #2Sub-CCE #9 PRB pair #m CCE #3 Sub-CCE #3 Sub-CCE #12 PRB pair #m CCE #4Sub-CCE #4 Sub-CCE #10 PRB pair #m CCE #5 Sub-CCE #5 Sub-CCE #15 PRBpair #n CCE #6 Sub-CCE #6 Sub-CCE #13 PRB pair #n CCE #7 Sub-CCE #7Sub-CCE #16 PRB pair #n CCE #8 Sub-CCE #8 Sub-CCE #14 PRB pair #n

It may be assumed that the PDCCH information is either mapped to 1, 2, 4or 8 control channel elements (i.e. the CCE aggregation size is 2^(i)).Hence, when mapping the PDCCH information of a receiving apparatus to2^(i)≦4 of the control channel elements, it may be ensured that thePDCCH information are all transmitted within one of the physicalresource block pairs, i.e. in a localized fashion. If the CCEaggregation level is higher than 4, i.e. all 2³=8 control channelelements are used to carry the PDCCH information of a receivingapparatus, adjacent physical resource block pairs (i.e. n=m±1) may beused so that the PDCCH information is getting mapped to a localized setof subcarriers in the frequency domain. Alternatively, the alsonon-adjacent physical resource block pairs may form the R-PDCCH region,i.e. n≠m±1.

The terms “adjacent” and “nom-adjacent” may not necessarily refer toneighboring or not neighboring physical resource block pairs. Rather, alocalized mapping may be understood as to refer to a mapping of thePDCCH information to resource block pairs that are within the coherencebandwidth of the channel (such that the channel conditions channelconditions within the two resource blocks are dependent from eachother), while a distributed mapping of the PDCCH information may beunderstood as to refer to a mapping of the PDCCH information to resourceblock pairs that are larger than or equal to the coherence bandwidth ofthe channel (such that the channel conditions channel conditions withinthe two resource blocks are independent from each other).

FIG. 13 and Table 4 show the combination of sub-control channel elementsto obtain a distributed mapping of control channel elements.

TABLE 4 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #14 PRB pairs #m & #n CCE #2 Sub-CCE#2 Sub-CCE #13 PRB pairs #m & #n CCE #3 Sub-CCE #3 Sub-CCE #16 PRB pairs#m & #n CCE #4 Sub-CCE #4 Sub-CCE #15 PRB pairs #m & #n CCE #5 Sub-CCE#5 Sub-CCE #10 PRB pairs #m & #n CCE #6 Sub-CCE #6 Sub-CCE #9 PRB pairs#m & #n CCE #7 Sub-CCE #7 Sub-CCE #12 PRB pairs #m & #n CCE #8 Sub-CCE#8 Sub-CCE #11 PRB pairs #m & #n

As can be seen from FIG. 13 and Table 4 the control channel elements ina distributed mapping comprise respective pairs of sub-control channelelements from the first group and sub-control channel elements of thesecond group located in different physical resource block pairs. Thisway the control channel elements are always “distributed” across thephysical resource block pairs.

It should be further noted that within each physical resource block pair#m and #n, CRS and/or DM-RS is provided in the some predefined resourceelements that are used by the receiving apparatus for channelestimation. CRS may for example be used when no beamforming is appliedfor the PDCCH information signaled in the R-PDCCH region. DM-RS may beused in a sub-frame for transmitting the beamforming is applied to thetransmission of the PDCCH information in the R-PDCCH region on the airinterface.

The number of DM-RS signals provided in the physical resource blockpairs, respectively the control channel elements may imply an upperlimit on the number of receiving apparatus(es) to which the controlchannel elements within a R-PDCCH region can be assigned (assuming thatthe R-PDCCH regions of multiple transmitting apparatuses is overlappingor identical). The DM-RS layers are receiving apparatus specific and maybe required for demodulation of the data signaled within the assignedphysical resources on the downlink. Therefore, each receiving apparatusthat is to receive data within a given physical resource block pair ofthe R-PDCCH region may require a own DM-RS to be present in the controlchannel element(s) assigned to which the PDCCH information istransmitted.

If there are four antenna ports for DM-RS transmission configured at thetransmitting apparatus, four DM-RS layers are available. The DM-RSsignals from the four layers are orthogonal to each other. If onephysical resource block pair is divided into four control channelelements as shown for example in FIG. 12 or FIG. 13, each controlchannel element can be linked to one DM-RS layer for demodulation.Accordingly, the control channel elements in each physical resourceblock pair of the R-PDCCH region can be assigned up to four receivingapparatus(es).

If only two antenna ports are available for DM-RS transmission, therecan only be two DM-RS layers. In this case, one possibility is that eachphysical resource block pair is divided into two control channel element(see for example FIG. 21 and FIG. 22) and each control channel elementis linked to one DM-RS layer. Hence, the control channel elements ineach physical resource block pair of the R-PDCCH region can be assignedto one or two receiving apparatus(es) only.

Another possibility is that each physical resource block pair is stilldivided into four control channel elements, but two control channelelements are linked to one DM-RS layer, respectively receivingapparatus. Accordingly, in this example the CCE aggregation level sizemay be restricted to be at least two control channel elements perreceiving apparatus and physical resource block pair.

For one control channel element (i.e. a combination of sub-controlchannel elements), the DM-RS layer may be chosen such that the number ofDM-RS signals that are signaled in each control channel element ismaximized. In the example shown in FIG. 12 and FIG. 13, all controlchannel elements comprise resource elements with DM-RS signals of allfour layers.

Control channel elements #1, #2, #5 and #6 comprise four resourceelements carrying DM-RS signals of layer 1 and 2 and two resourceelements carrying DM-RS signals for layer 3 and 4. Accordingly, thesecontrol channel elements may be linked to DM-RS layer 1 or 2. Controlchannel elements #3, #4, #7 and #8 comprise two resource elementscarrying DM-RS signals of layer 1 and 2 and four resource elementscarrying DM-RS signals for layer 3 and 4, so that it is advantageous tolink same to DM-RS layer 3 and 4. Accordingly, in a further embodimentof the invention, the transmitting apparatus ensures that the PDCCHinformation of a receiving apparatus is mapped to control channelelement(s) linked to the DM-RS layer associated to the receivingapparatus, so that the number of DM-RS signals of the given DM-RS layerper control channel element can be maximized.

Furthermore, mapping of the PDCCH information to the control channelelements in the R-PDCCH region depends on the number of control channelelements available therein and the CCE aggregation size. It may beexemplarily assumed that the PDCCH information for a receiving apparatusis either mapped to 1, 2, 4 or 8 control channel elements.

For CCE aggregation level 1, i.e. the PDCCH information of a receivingapparatus is mapped to one control channel element of the R-PDCCHregion, and assuming a localized mapping of the PDCCH information to thecontrol channel element (i.e. a localized search space for the receivingapparatus), the two sub-CCEs that form a control channel element arechosen from the same physical resource block pair. In the distributedmapping of the PDCCH information to the control channel element (i.e. adistributed search space for the receiving apparatus), the two sub-CCEsthat form a control channel element are chosen from different physicalresource block pairs.

For CCE aggregation level 2, i.e. the PDCCH information of a receivingapparatus is mapped to two control channel elements of the R-PDCCHregion, and assuming a localized mapping of the PDCCH information to thetwo control channel elements (i.e. a localized search space for thereceiving apparatus), both control channel elements are located in thesame physical resource block pair.

In the distributed mapping of the PDCCH information to the two controlchannel elements (i.e. a distributed search space for the receivingapparatus), both control channel elements are located in differentphysical resource block pairs. Furthermore, the control channel elementsmay be consistently distributed in frequency domain. For example, inFIG. 12 a distributed mapping of PDCCH information to the two controlchannel elements by the transmitting apparatus can be obtained bymapping the PDCCH information—for example—to CCE #1 and CCE #5. Inaddition, the control channel elements may be formed so that eachcontrol channel element is formed by sub-CCEs of multiple physicalresource block pairs. In FIG. 13, each control channel element has asub-CCE of physical resource block pair #m and a sub-CCE of physicalresource block pair #n, so that a distributed mapping is obtained(irrespective of the actual CCE aggregation size).

For CCE aggregation level 4, i.e. the PDCCH information of a receivingapparatus is mapped to four control channel elements of the R-PDCCHregion, if one physical resource block pair is divided into two controlchannel elements—see for example the discussion of FIG. 18 to FIG. 20below —, the two physical resource block pairs will be used for onesignaling the PDCCH information. In this example, a localized ordistributed mapping of the PDCCH information may be achieved byconfiguring the two physical resource block pairs either as adjacentphysical resource block pairs or non-adjacent physical resource blockpairs (as mentioned before, “adjacent” and “non-adjacent” may be definedrelative to the coherence bandwidth of the channel).

If one physical resource block pair is divided into four control channelelements, a localized and distributed mapping of the PDCCH informationto the four control channel elements may be obtained in a similarfashion as described fro CCE aggregation level 2.

For CCE aggregation level 8, i.e. the PDCCH information of a receivingapparatus is mapped to eight control channel elements of the R-PDCCHregion, if one physical resource block pair is divided into two controlchannel elements, two physical resource block pairs will not be enoughfor transmitting the PDCCH information to the receiving apparatus.Hence, the transmitting apparatus may map only one half of the PDCCHinformation to the two physical resource block pairs. Anotherpossibility is to configure four physical resource block pairs as thebasic R-PDCCH region size.

Furthermore, if one physical resource block pair is divided into fourcontrol channel elements, the two physical resource block pairs withinthe R-PDCCH region are sufficient to carry the PDCCH information. Inthis case, a localized or distributed mapping of the PDCCH informationmay be achieved by configuring the two physical resource block pairseither as adjacent physical resource block pairs or non-adjacentphysical resource block pairs (as mentioned before, “adjacent” and“non-adjacent” may be defined relative to the coherence bandwidth of thechannel).

One advantage of the use of sub-control channel elements is theirflexibility in combining same according to a known scheme. This may forexample allow the transmitting apparatus to switch between localized anddistributed mapping of the PDCCH information of the receiving apparatusto the R-PDCCH region. Furthermore, by a smart combination of thesub-control channel elements, also a simultaneous localized anddistributed mapping can be realized, which may be advantage if pluralreceiving apparatuses have the same or overlapping R-PDCCH regions. FIG.14 shows an exemplary combination of pairs of sub-control channelelements (sub-CCEs) of FIG. 11 to form eight control channel elements(CCEs) allowing fro a localized and a distributed mapping of the R-PDCCHinformation according to an embodiment of the invention. A smartcombination of sub-CCEs may allow to re-use physical resource blocks forother purposes, e.g. PDSCH transmissions, if none of the control channelelements are used for mapping a R-PDCCH information.

The control channel elements of FIG. 14 are obtained by a combination ofsub-control channel element pairs as shown in Table 5.

TABLE 5 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #15 PRB pairs #m & #n CCE #2 Sub-CCE#2 Sub-CCE #16 PRB pairs #m & #n CCE #3 Sub-CCE #3 Sub-CCE #12 PRB pair#m CCE #4 Sub-CCE #4 Sub-CCE #11 PRB pair #m CCE #5 Sub-CCE #5 Sub-CCE#14 PRB pair #n CCE #6 Sub-CCE #6 Sub-CCE #13 PRB pair #n CCE #7 Sub-CCE#7 Sub-CCE #9 PRB pairs #m & #n CCE #8 Sub-CCE #8 Sub-CCE #10 PRB pairs#m & #n

Using the mapping scheme shown in FIG. 14 and Table 5, for example, adonor eNodeB could assign two relay nodes the same R-PDCCH regionand—assuming a CCE aggregation size of four—map the PDCCH information ofone relay node in a localized fashion and the PDCCH information of theother relay node in a distributed fashion to the R-PDCCH resources.

FIG. 15 exemplifies another division of two physical resource blockpairs #m and #n of a R-PDCCH region into 16 sub-control channel elements(sub-CCEs) according to an exemplary embodiment of the invention. Theexample shown in FIG. 15 is similar to that of FIG. 11 described above,except for the sub-control elements not being divided in the time domainat the slot boundaries of the sub-frame. Instead, in this example, theN_(symb) ^(R-PDCCH) OFDM symbols in the time domain are evenlydistributed to the respective first group and second group ofsub-control channel elements. The sub-control channel elements in thefirst group thus have either k₁=13 or k₂=15 resource elements forconveying the control information, i.e. which are not used for referencesignals. The sub-control channel elements in the second group haveeither l₁=12 or l₂=14 resource elements for conveying the controlinformation, which again yields a control channel element size ofj=k₁+l₂=k₂+l₁=27 resource elements that are available to convey thePDCCH information for the receiving apparatus.

FIG. 16 shows an exemplary combination of pairs of sub-control channelelements (sub-CCEs) of FIG. 15 to form 8 control channel elements (CCEs)using a localized mapping of the R-PDCCH information according to anembodiment of the invention. A distributed mapping of the R-PDCCHinformation may be obtained in a similar fashion as shown in FIG. 13 andas has been described above. Also for the exemplary division of theR-PDCCH region as shown in FIG. 16, the control channel elements may beformed as described with respect to FIGS. 12 to 14 and Table 2 to Table5 above.

While the example with reference to FIG. 11 to 16 have been exemplifiedusing a normal sub-frame as known from 3GPP-LTE (Release 8), the samedivisions and combinations as outlined with respect to FIGS. 12 to 14and Table 2 to Table 5 above may be used for a MBSFN sub-frame as shownin FIG. 9. FIG. 17 exemplifies a division of two physical resource blockpairs #m and #n of a R-PDCCH region of a MBSFN sub-frame intosub-control channel elements (sub-CCEs) according to an exemplaryembodiment of the invention. Essentially, the difference to the normaldivision of the normal sub-frame as discussed with respect to FIG. 11and FIG. 16 above is that the MBSFN sub-frame does not comprise commonreference signals. Hence, in the exemplary division of the MBSFNsub-frame into sub-control channel elements the size of the sub-controlchannel elements in the first group is either k₁=11 or k₂=13 resourceelements for conveying the control information, i.e. which are not usedfor reference signals. The sub-control channel elements in the secondgroup have either l₁=17 or l₂=19 resource elements for conveying thecontrol information, which yields a control channel element size ofj=k₁+l₂=k₂+l₁=30 resource elements that are available to convey thePDCCH information for the receiving apparatus.

It should be further noted that the above outlined division of theR-PDCCH region in the frequency and time domain may also be applied inscenarios, where there is no control channel region provided in thefirst OFDM symbols of the sub-frame, as for example shown in FIG. 28. Asone may still assume the reference signal pattern to be unchanged adivision in the frequency domain into blocks of N_(SC) ^(CCE)=3 appearsfeasible to again obtain sub-control channel elements in the first groupthat have either k₁ or k₂ resource elements for conveying the controlinformation, and sub-control channel elements in the second group thathave either l₁ or l₂ resource elements for conveying the controlinformation. This way, the control channel elements can be easily formedby pairs of sub-control channel elements from the first and secondgroup, so that a control channel element size of k₁+l₂=k₂+l₁ is obtained(where k₁≠k₂ and l₁≠l₂). Furthermore, also in cases where the R-PDCCHregion is not immediately starting after the control channel region(PDCCH region), as shown in FIG. 27, the same division of the R-PDCCHregion as outlined above with respect to FIG. 11 to 17 may be used.

In the previous examples a division of the control channel region intime domain and frequency domain has been used. Other embodimentsencompass the division of the control channel region in frequency domainonly. FIG. 18 exemplifies another division of two physical resourceblock pairs #m and #n of a R-PDCCH region into eight sub-control channelelements (sub-CCEs) according to an exemplary embodiment of theinvention using a FDM approach. The R-PDCCH region is divided intoblocks of N_(SC) ^(CCE)=3 subcarriers, so that overall, there are eightsub-control channel elements obtained.

Each sub-channel element spans N_(SC) ^(CCE)=3 subcarriers in thefrequency domain and all N_(symb) ^(R-PDCCH) OFDM symbols of the R-PDCCHregion in the time domain. Again, pairs of the sub-control channelelements #1 to #8 are combined to respective control channel elements,such that all four control channel elements resulting from thiscombination are equal in size. The size of the sub-control channelelements is either k₁=25 (sub-CCEs 1#, #4, #5, #8) or k₂=27 (sub-CCEs#2, #3, #6, #7) resource elements for conveying the control information,i.e. which are not used for reference signals. Accordingly, by combiningsub-control channel elements of size k₁=25 and k₂=27, the resultingcontrol channel elements yield a constant size of 52 resource elementsfor elements for conveying the control information. FIG. 19 and FIG. 20show exemplary combinations of pairs of sub-control channel elements(sub-CCEs) of FIG. 18 to form the four resulting control channelelements (CCEs) facilitating a localized, respectively distributed.Table 6 exemplifies the sub-CCE combinations of the structure of theR-PDCCH region of FIG. 19. The two sub-control channel elements of thesame physical resource block pairs are combined respectively to obtain alocalized mapping of the PDCCH information.

TABLE 6 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #2 PRB pair #m CCE #2 Sub-CCE #3Sub-CCE #4 PRB pair #m CCE #3 Sub-CCE #5 Sub-CCE #6 PRB pair #n CCE #4Sub-CCE #7 Sub-CCE #8 PRB pair #n

Table 7 exemplifies the sub-CCE combinations of the structure of theR-PDCCH region of FIG. 20. The two sub-control channel elements of thedifferent physical resource block pairs are combined respectively toobtain a distributed mapping of the PDCCH information.

TABLE 7 Control Sub-control Sub-control Channel channel element channelelement Resource block Element of first group of second group pairsutilized CCE #1 Sub-CCE #1 Sub-CCE #5 PRB pairs #m & #n CCE #2 Sub-CCE#2 Sub-CCE #6 PRB pairs #m & #n CCE #3 Sub-CCE #3 Sub-CCE #7 PRB pairs#m & #n CCE #4 Sub-CCE #4 Sub-CCE #8 PRB pairs #m & #n

Alternatively, for CCE aggregation sizes larger than 1, CCEs as shown inFIG. 19 and Table 6 that are located on different physical resourceblock pairs could be used for signaling the PDCCH information in adistributed fashion.

As mentioned above, the physical resource block pairs #m and #n may ormay not be adjacent to each other within the frequency domain.Furthermore, in a likewise fashion, also R-PDCCH regions comparing morethan two physical resource block pairs may be structured into controlchannel elements.

Furthermore, in another exemplary embodiment of the invention shows howmore than two sub-control channel elements may be combined into controlchannel elements. This exemplary embodiment is assuming the sub-controlchannel division as shown in FIG. 11. FIGS. 21 and 22 show exemplarycombinations of pairs of sub-control channel elements (sub-CCEs) of FIG.11 to form four control channel elements (CCEs) using a localized,respectively distributed mapping of the R-PDCCH information according toan embodiment of the invention. In this example, four sub-controlchannel elements are combined to form four control channel elements ofequal size. Table 8 shows the sub-control channel elements that form therespective four control channel elements for the localized mapping ofFIG. 21. Also in this example all control channel elements are formed bysub-control channel elements of the same physical resource block pair.

TABLE 8 Sub-control Sub-control Sub-control Sub-control Control channelchannel channel channel Channel element 1 of element 2 of element 3 ofelement 4 of Element first group first group second group second groupCCE #1 Sub-CCE #1 Sub-CCE #3 Sub-CCE #10 Sub-CCE #12 CCE #2 Sub-CCE #2Sub-CCE #4 Sub-CCE #9 Sub-CCE #11 CCE #3 Sub-CCE #5 Sub-CCE #7 Sub-CCE#14 Sub-CCE #16 CCE #4 Sub-CCE #6 Sub-CCE #8 Sub-CCE #13 Sub-CCE #15

Table 9 shows the sub-control channel elements that form the respectivefour control channel elements for the distributed mapping of FIG. 22.For obtaining a distributed mapping, the sub-control channel elementsthat form a respective control channel element are located on distinctphysical resource block pairs.

TABLE 9 Sub-control Sub-control Sub-control Sub-control Control channelchannel channel channel Channel element 1 of element 2 of element 3 ofelement 4 of Element first group first group second group second groupCCE #1 Sub-CCE #1 Sub-CCE #5 Sub-CCE #10 Sub-CCE #14 CCE #2 Sub-CCE #2Sub-CCE #6 Sub-CCE #9 Sub-CCE #13 CCE #3 Sub-CCE #3 Sub-CCE #7 Sub-CCE#12 Sub-CCE #16 CCE #4 Sub-CCE #4 Sub-CCE #8 Sub-CCE #11 Sub-CCE #15

FIG. 23 shows another division of a control channel region within asub-frame in a FDM fashion according to a further exemplary embodimentof the invention. In this example—in line with the example shown in FIG.29 discussed previously herein —, it is assumed that the sub-frame donot contain a PDCCH region within the firsts OFDM symbols of thesub-frame. Instead, a PDCCH region carrying the PDCCH information forthe receiving apparatus is assigned to the receiving apparatus (e.g. auser equipment or a relay node) by the transmitting apparatus (e.g. basestation or relay node). The PDCCH regions of the receiving apparatus(es)within a radio cell controlled by the transmitting apparatus may overlapor may even be identical. The PDDCH region may be considered a searchspace in which the respective receiving apparatus is expecting toreceive the control signaling (e.g. downlink and/or uplink resourceassignments) from the transmitting apparatus.

In this exemplary embodiment on the invention, the PDCCH region isspanning the OFDM symbols of the first slot of the sub-frame. Hence,N_(symb) ^(R-PDCCH)=N_(symb) in this exemplary embodiment. The PDCCHregion of the receiving apparatus is split in the frequency domain inblocks of N_(SC) ^(CCE)=3 subcarriers, so that overall, there are eightsub-control channel elements obtained by the division. Each sub-channelelement spans N_(SC) ^(CCE)=3 subcarriers in the frequency domain andall N_(symb) ^(R-PDCCH) OFDM symbols of the PDCCH region in the timedomain.

Again, pairs of the sub-control channel elements #1 to #8 are combinedto respective control channel elements, such that all four controlchannel elements resulting from this combination are equal in size. Thesize of the sub-control channel elements is either k₁=15 (sub-CCEs 1#,#4, #5, #8) or k₂=17 (sub-CCEs #2, #3, #6, #7) resource elements forconveying the control information, i.e. which are not used for referencesignals. Accordingly, by combining sub-control channel elements of sizek₁=15 and k₂=17, the resulting control channel elements yield a constantsize of 32 resource elements for elements for conveying the controlinformation. The sub-control channel elements may be combined pair-wise,by combining sub-control elements of sizes k₁=15 and k₂=17 with eachother in a similar fashion as has been discussed above with respect toFIG. 19 and FIG. 20 as well as Table 6 and Table 7.

In the previous paragraphs, several different exemplary embodiments ofthe structure of a R-PDCCH region and PDCCH region for signaling PDCCHinformation from a transmitting apparatus to a receiving apparatus havebeen discussed. In the following, the operation of the transmittingapparatus and the receiving apparatus will be described in furtherdetail. The transmitting apparatus may be either a base station (e.g. aeNodeB) or a relay node. The receiving apparatus may be a relay node ora user equipment. Furthermore it should be noted that the transmittingapparatus may of course serve more than one receiving apparatus in itscoverage area and comprises a scheduling function for assigning uplinkor downlink resources to the transmitting apparatus(es) by means ofsignaling PDCCH information on the (R-)PDCCH region.

As discussed above the transmitting assigning to a receiving apparatus acontrol channel region ((R-)PDCCH region) within sub-frames forsignaling PDCCH information to the receiving apparatus. The (R-)PDCCHregion is structured into control channel elements according to one ofthe various embodiments of the invention discussed above. The physicalresources of the (R-)PDCCH region may be configured on dynamically orsemi-statically or may be predefined. For a semi-static configurationthe transmitting apparatus may use radio resource control signaling,i.e. may send the parameters that describe the time and frequencyresource of the (R-)PDCCH region to the receiving apparatus by means ofan RRC signaling message. The (R-)PDCCH region may also be configured bythe transmitting apparatus by means of system information broadcast inthe radio cell of the transmitting apparatus. For example, theconfiguration information may be sent in one of the system informationblocks broadcast by the transmitting apparatus. Another possibility isto statically define the R-)PDCCH region, for example by pre-defining itin a specification.

In one embodiment the configuration information made available to thereceiving apparatus include an indication of the physical resource blockpairs that define the (R-)PDCCH region. If the extend of the (R-)PDCCHregion in the time domain is not predefined or implicit from sub-frameboundaries or other parameters such as the PCFICH value, theconfiguration information may further include an indication of the OFDMsymbols of the sub-frame that define the (R-)PDCCH region in the timedomain. For example, the transmitting apparatus may indicate in theconfiguration information the symbol index n_(start) ^(R-PDCCH) of theOFDM symbol at which the first symbol of the (R-)PDCCH region.Optionally, the configuration information may also comprise a symbolindex n_(end) ^(R-PDCCH) for indicating the last symbol of the (R-)PDCCHregion or the size of (R-)PDCCH region in terms of number of OFDMsymbols.

The transmitting apparatus generates a sub-frame to be sent in thedownlink. The sub-frame may comprise control information and user dataof multiple receiving apparatuses. The sub-frame as such spans alldownlink component carriers available to the base station, but islogically divided into plural OFDM symbols in the time domain onrespective component carriers in the frequency domain. The componentcarriers in the downlink span a certain range of sub-bands (subcarriers)that define the bandwidth of the respective component carrier. Thesub-frame structure may be as such structured as shown in FIG. 8 or FIG.9 and comprises several reference signals that are transmitted onrespective resource elements in a pre-determined pattern.

The transmitting apparatus generates PDCCH information for one or morereceiving apparatuses. The PDCCH information may be provided in form ofa know downlink control information (DCI) format. The transmittingapparatus maps the PDCCH information for transmission to one or morecontrol channel elements in the (R-)PDCCH region that is configured fora respective receiving apparatus within a sub-frame on the downlink.Please note that the transmitting apparatus may use a distributed orlocalized mapping scheme for mapping the PDCCH information to the(R-)PDCCH region using one of the various (R-)PDCCH region structures asoutlined above. In one example, the PDCCH information is mapped to 2^(i)of the control channel elements defined in the (R-)PDCCH region, whereiniε{0,1,2,3} or iε{0,1,2,3,4}.

In order to be able to address the different PDCCH information that issignaled by a transmitting apparatus to the correct receiving apparatus,a receiving apparatus-specific (i.e. UE-specific or relay node-specific)RNTI (Radio Network Terminal Identifier) is implicitly included in thePDCCH information signaled in the (R-)PDDCH region by masking the CRC ofthe encoded PDCCH information with the RNTI. On the receiving apparatusside, if decoding of the coded PDCCH information is successful, thereceiving apparatus detects the PDCCH information to be destined to itby checking whether the CRC on the decoded PDCCH information using the“unmasked” CRC (i.e. after removing the masking using the RNTI) issuccessful. Please note that the masking of the CRC code is performed byscrambling the CRC with the RNTI.

Hence, the CRC of coded PDCCH information is scrambled/masked with arespective RNTI of the transmitting apparatus and the coded PDCCHinformation and the masked CRC code (CRC attachment) is mapped to theCCEs within the (R-)PDCCH region on the downlink as outlined in one ofthe different embodiments of the (R-)PDCCH region structure above.Finally the transmitting apparatus transmits the sub-frame on thedownlink.

The receiving apparatuses attempt to detect the control information intheir assigned (R-)PDCCH region using so-called “blind decoding”. Thismeans that there is no associated control signaling that would indicatethe CCE aggregation size or modulation and coding scheme for the PDCCHinformation signaled in the downlink, but the user equipments/relaynodes test for all possible combinations of CCE aggregation sizes andmodulation and coding schemes, and confirms that successful decoding ofa PDCCH information based on the RNTI that is used to mask the CRC fieldthat is attached to the PDCCH information.

The receiving apparatuses may be assumed to perform a blind detection ona set of (R-)PDCCH candidates for the PDCCH information in every non-DRXsub-frame, where blind detection implies attempting to decode each ofthe (R-)PDCCH candidate in the set according to some set of themonitored (R-)PDCCH formats (Downlink Control Information (DCI)formats). The set of (R-)PDCCH candidates to monitor may be defined interms of search spaces, where a search space at each CCE aggregationlevel Lε{1,2,4,8} is defined by a set of PDCCH candidates. The use ofsearch spaces may be particularly useful in situations where multiplereceiving apparatuses share a common (R-)PDCCH region of larger extend,so that it may be desirable to limit the search for PDCCH information bythe respective receiving apparatuses to respective sub-regions (i.e. thesearch space) to thereby reduce the number of blind decoding attempts.

As explained before, to limit complexity of the blind decoding, thereceiving apparatuses may be allocated to one or more search spaces inwhich they expect their PDCCH information. Within the same (R-)PDCCHregion, two types of search spaces may be defined: one is a localizedsearch space and the other is distributed a search spaces. In localizedsearch space, at each CCE aggregation level, the CCEs composing thePDCCH candidates are more localized in frequency domain. In distributedsearch space, at each aggregation level, the CCEs composing the PDCCHcandidates are distributed in frequency domain. A receiving apparatusmay be configured to monitor a localized search space only, adistributed search space only or a localized and distributed searchspace simultaneously. Which search space(s) are to be monitored by arespective receiving apparatus may be for example configured by thetransmitting apparatus by means of RRC signaling,

The receiving apparatus blind decodes the payload size of the (R-)PDCCHmessage and uses its RNTI to descramble the CRC. Based on thedescrambled CRC information, the receiving apparatus determines whetherthe message payload (i.e. decoded PDCCH information) has beensuccessfully decoded and is destined to the receiving apparatus.

The PDCCH information for the receiving apparatus may for examplecontain an uplink and/or downlink resource assignment for the receivingapparatus. In one embodiment of the invention, the resource assignmentsfor uplink and downlink indicate the assigned physical resources ondownlink, respectively uplink, in terms of physical resource blocks, themodulation and coding scheme of the transport block to bereceived/transmitted on the indicated downlink/uplink resources, and thetransport block size. Furthermore, in case the transport block istransmitted using a HARQ protocol, further HARQ related information suchas the new data indicator (NDI) and/or the HARQ process identifier mayalso be included in the resource assignments. If cross carrierscheduling and carrier aggregation is employed, the resource assignmentsmay also comprise a carrier identifier field (CIF) that indicates thedownlink respectively uplink component carrier on which the physicalresources are assigned.

In case of a downlink resource assignment, the resources for thetransmission of the transport block may be transmitted on the samedownlink sub-frame as the downlink resource assignment. Accordingly, thereceiving apparatus will try to receive and decode the downlinktransport block. In case of an uplink resource assignment, the receivingapparatus generates a transport block according to the parameters(modulation and coding scheme and transport block size) and transmitsthe transport block on the assigned uplink resources.

Another embodiment of the invention is related to the allocation of thephysical resource block pairs that belong to the (R-)PDCCH region to thereceiving apparatus. In this exemplary embodiment, it is proposed to usean allocation method similar to the (Distributed Virtual Resource Block)DVRB allocation method known from 3GPP LTE (Release 8). In 3GPP LTE(Release 8), four types of resource allocation are used for allocationphysical resources in the PDSCH region of sub-frame. One of these fourallocation types is the DVRB allocation. DVRB allocation is advantageousfor distributed mapping of small data.

Normally (R-)PDCCH region for each receiving apparatus is very small,only a couple of resource blocks. Therefore, it is proposed in thisembodiment a resource allocation scheme similar to DVRB is used for theallocation of the physical resource block pairs that belong to the(R-)PDCCH region. In DVRB allocation, a number of contiguous DistributedVirtual Resource Blocks (DVRBs) is allocated to the scheduled receivingapparatus. The DVRBs are identified by their indices. For transmission,the DVRBs are mapped to “real” physical resource blocks according to agiven mapping rule. The mapping between DVRBs to physical resourceblocks as defined in the 3GPP TS 23.213, “Physical layer procedures(Release 8)”, version 8.8.0, section 7.1.6 (available athttp://www.3gpp.org and incorporated herein by reference). According tothis embodiment, the (R-)PDCCH region resources may also be indicated asvirtual resource blocks that are mapped to physical resource blocks fortransmission. The mapping follows some rules so that DVRB index isdistributed across the bandwidth and achieve 4^(th) order diversity. Inorder to support localized and distributed mapping simultaneously, itmay be advantageous to allocated (R-)PDCCH region on distributedphysical resource blocks. DVRB allocation for (R-)PDCCH region mayensure that the resource blocks within the (R-)PDCCH region aredistributed in the frequency domain.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors) that aresuitably controlled by executable instructions that cause the computingdevice to perform the functions according to the different embodimentsof the invention described herein.

For example the transmitting apparatus's scheduling function, thesignaling mechanisms for configuring the (R-)PDCCH region, the sub-framegeneration, the mapping of PDCCH information to appropriate OFDM symbolsof the (R-)PDCCH region in the sub-frame according to given mappingrules, etc. may be for example implemented in hardware and/or software.Similarly, the processing of the received sub-frames at the receivingapparatuses may at least partly implemented in hardware and/or software.A computing device or processor may for example be general purposeprocessors, digital signal processors (DIP), application specificintegrated circuits (ASICS), field programmable gate arrays (FAGAN) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer-readable storage media,for example RAM, EPROM, EPSOM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

Most of the embodiments have been outlined in relation to a 3GPP-basedarchitecture of a communication system and the terminology used in theprevious sections mainly relates to the 3GPP terminology. However, theterminology and the description of the various embodiments with respectto 3GPP-based architectures are not intended to limit the principles andideas of the inventions to such systems only.

Also the detailed explanations given in the Technical Background sectionabove are intended to better understand the mostly 3GPP specificexemplary embodiments described herein and should not be understood aslimiting the invention to the described specific implementations ofprocesses and functions in the mobile communication network.Nevertheless, the concepts and sub-frame structures proposed herein maybe readily applied in the architectures described in the TechnicalBackground section. Furthermore, the concept of the invention may bealso readily used in the LTE-A RAN currently discussed by the 3GPP.

In the previous paragraphs various embodiments of the invention andvariations thereof have been described. It would be appreciated by aperson skilled in the art that numerous variations and/or modificationsmay be made to the present invention as shown in the specificembodiments without departing from the spirit or scope of the inventionas broadly described.

The invention claimed is:
 1. A transmission method for mapping physicaldownlink control channel information for a receiving apparatus tocontrol channel elements (CCEs) of a control channel region of asub-frame of a 3GPP-based based communication system using OFDM in thedownlink, the method comprising the following steps performed by atransmitting apparatus: configuring a plurality of CCEs in anextended-physical downlink control channel (extended-PDCCH) regiondefined in a physical downlink shared channel (PDSCH) region within asub-frame for signaling downlink control information to the receivingapparatus, the sub-frame comprising a plurality of physical resourceblock pairs, wherein several sub-control channel elements (sub-CCEs)having different sizes are combined to form CCEs of equal size in bothof a localized mapping scheme where each CCE consists of a plurality ofsub-CCEs belonging to a single resource block pair and a distributedmapping scheme where each CCE consists of a plurality of sub-CCEsbelonging to the plurality of physical resource block pairs, each sizebeing a number of resource elements (REs) excluding REs for transmittingreference signals; mapping the downlink control information to at leastone of the plurality of CCEs configured in the extended-PDCCH region;and transmitting the mapped downlink control information.
 2. Thetransmission method according to claim 1, wherein the downlink controlinformation is mapped to 2^(i)≦2. N_(SC)/N_(SC) ^(CCE) of the CCEsconfigured in the extended-PDCCH region, wherein i ε{0,1,2,3, . . .}. 3.The transmission method according to claim 1, further comprising thesteps of generating a sub-frame comprising the downlink controlinformation for the receiving apparatus mapped to the extended-PDCCHregion and transmitting the sub-frame to the receiving apparatus.
 4. Thetransmission method according to claim 1, further comprising the stepsof: determining CRC code for the downlink control information for thereceiving apparatus, masking the CRC code with a receivingapparatus-specific identifier, and appending the masked CRC code to thedownlink control information for the receiving apparatus within a CRCfield, wherein the transmitting apparatus maps the coded downlinkcontrol information for the receiving apparatus to one or more CCEs ofthe extended-PDCCH region together with the CRC field comprising themasked CRC code.
 5. The transmission method according to claim 1,wherein the plurality of physical resource block pairs for signaling thephysical control channel information to the receiving apparatus is:configured by the transmitting apparatus by means of radio resourcecontrol signaling, configured by the transmitting apparatus by means ofsystem information broadcast in the radio cell of the transmittingapparatus, and/or pre-determined.
 6. The transmission method accordingto claim 1, wherein a same extended-PDCCH region or partly overlappingextended-PDCCH regions is/are assigned to plural receiving apparatuses,including the receiving apparatus.
 7. A reception method, comprising:configuring a plurality of control channel elements (CCEs) in anextended-physical downlink control channel (extended-PDCCH) regiondefined in a physical downlink shared channel (PDSCH) region within asub-frame for signalling downlink control information to a receivingapparatus, the sub-frame comprising a plurality of physical resourceblock pairs, receiving a signal including downlink control informationmapped to at least one of the plurality of CCEs configured in theextended-PDCCH region within a sub-frame from a transmitting apparatus,wherein several sub-control channel elements (sub-CCEs) having differentsizes are combined to form CCEs of equal size in both of a localizedmapping scheme where each CCE consists of a plurality of sub-CCEsbelonging to a single resource block pair and a distributed mappingscheme where each CCE consists of a plurality of sub-CCEs belonging tothe plurality of physical resource block pairs, each size being a numberof resource elements (REs) excluding REs for transmitting referencesignals, and decoding the received signal to obtain the downlink controlinformation for the receiving apparatus.
 8. The reception methodaccording to claim 7, further comprising the steps of performing withinthe extended-PDCCH region of the receiving apparatus, a blind detectionof downlink control information comprised in one or more of the CCEs,wherein the blind detection comprises: obtaining a masked CRC code froma CRC field within the CCE(s) conveying the downlink controlinformation, de-masking the masked CRC code with a receivingapparatus-specific temporary identifier, and verifying successful blinddetection of the control information for the receiving apparatus basedon the CRC code.
 9. The reception method according to claim 7, furthercomprising the step of receiving from a transmitting apparatus a controlchannel assignment message for configures the plurality of physicalresource block pairs for signalling the downlink control information tothe receiving apparatus.